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Open Cell Spray Foam to Roof Steel – When Insulation is Done Wrong

Open Cell Spray Foam to Roof Steel – When Insulation is Done Wrong

Reader JOSH in FARMINGTON writes:

“I recently had a pole barn built and after doing a lot of research, went with 5″ of open cell under the roof and on the gables. I did not have any kind of vapor barrier, as I was worried the weight of the foam would cause it to sag and create air gaps where moisture could accumulate. I checked with the metal supplier to confirm it would not cause warranty issues and they said it would not. I am somewhat 2nd guessing the open cell, but I did it because I want to make sure I see any leaks that might occur from the exposed fasteners. I have not insulated the walls yet as I wanted to get all the electrical done. My plan was I would spray low expansion foam at the top and bottom of the metal sheets because right now there are no foam seals so you can actually see daylight even with the metal rat guards. To seal these up I want to use Great Stuff Pond & Stone foam. It’s black to match the trim in case it pushes out, it’s waterproof, it’s low expansion, and it’s UV rated. Then I was going to put 1.5″ foam board between the purlins, sliding it behind the posts. Following up with covering both with another sheet of 2″ foam board and use tape at the seams and some more foam at the posts. My thought is this would create a good vapor barrier, but I’m second guessing that now. For one reason, I don’t know how I’d seal things up above the header. They used a double 2×10 on each side of the post to act as the header. I do not plan to put a ceiling up and I will have a split system with a gas furnace installed soon to keep the space tempered between 60-80. I’ll heat it up or cool it down as needed when I’m using it. Do you see any issues with this setup? I’m a little worried about not having a vapor barrier on the roof. In Arkansas, we have all seasons, but it stays pretty muggy.”

My first concern is your open cell spray foam against roof steel. You have an application here I would never recommend. Open cell spray foam allows moisture to pass through, so you are going to end up with moisture condensing on underside of roof steel. I do not have a solution at hand for this – perhaps whoever installed your spray foam has some ideas.

As you propose to insulate your walls, you are creating a vapor barrier – meaning your walls will ‘dry to inside’ – adding even more moisture to potentially cause a problem in your open cell roof insulation. I would remove steel siding from a wall at a time, then install a well-sealed housewrap. Fill insulation cavity with rockwool batts (as it is not affected by moisture), with an interior vapor barrier. Walls will now dry to outside.

Chances are you are going to need to mechanically dehumidify your building in order to minimize condensation from moisture hitting roof steel.

This entry was posted in Pole Barn Heating, Pole Barn Planning, Barndominium, Pole Barn Structure, Uncategorized, Ventilation, Insulation, Building Interior, Pole Barn Design, Roofing Materials, Constructing a Pole Building, Pole Building How To Guides and tagged , , , , , , on by .

Housewrap, Roof Insulation, and Ceiling Fasteners

This Wednesday the Pole Barn Guru answers reader questions about a home owner asking builder to install housewrap on the roof, the best solution to insulate underside of roof, and what the best fastener for screwing steel to ceiling or roof trusses would be.

DEAR POLE BARN GURU: Pole Barn Guru, thank you for your knowledge. I have a customer wanting house wrap around the exterior of a 30×40 pole barn. Is house wrap to be installed in between purlins and roof steel or will I need a radiant barrier to prevent condensation? Home owner says house wrap on the roof as well but I’m not sure if that’s the route he really wants to go. House wrap on side walls in between girts and side steel is also the best route correct?

Thank you for your kind words, they are much appreciated. Provided your client will not be doing closed cell spray foam on walls, use house wrap between girts and wall steel. For his roof, housewrap is totally incorrect, as it allows moisture to pass through and become trapped between wrap and roof steel – potentially causing premature degradation. If your client is not closed cell spray foaming directly to roof steel, then order your roof metal with an Integral Condensation Control factory applied (Dripstop, Condenstop or similar) https://www.hansenpolebuildings.com/2020/09/integral-condensation-control-2/. If roof steel has already been ordered (again assuming no closed cell spray foam being applied), then you do need some sort of a thermal break – such as a well-sealed radiant barrier.

 

DEAR POLE BARN GURU: Hi Mike, I built a 32’X40’X12′ pole building, (Shop) I used 1 1/2″ foam board on the inside walls, (on the inside of the girts) I can’t decide how I should insulate the underside of the roof. I have had a couple Spray Foam guy’s quote it , that’s pricy. Of course, the best R Value etc. at the most reasonable price is what I am looking for. In some of your post you have mentioned Rockwool that has gotten my attention. I see they make it up to R30. One thing that sticks in my mind is, my builder suggested not to use an insulation that will give insects a place to live. What would be your suggestion for underside of Roof insulation. Thank you. JIM in SPRING HILL

DEAR JIM: If your building has no current provision for controlling condensation on underside of roof steel, then two inches of closed cell spray foam applied directly to steel is your best insulation option. If you desire a greater R value, you can go thicker, or add open cell.

 

DEAR POLE BARN GURU: What screw is best for installing metal panels on the ceiling to wood trusses. MICHAEL in WENTZVILLE

DEAR MICHAEL: Most people are using #9 or #10 diameter 1″ screws. If you have ceiling framing 24 inches on center and want to utilize strength of ceiling liner panels to help transfer wind shear loads, then 1-1/2″ long diaphragm screws would be a better design solution.

This entry was posted in Roofing Materials, Pole Building How To Guides, Pole Barn Planning, Post Frame Home, Ventilation, Uncategorized, Insulation, Building Interior, Pole Barn Questions, Pole Barn Design, Pole Barn Heating and tagged , , , , , , , , on by .

Screw Penetration, Truss Carrier Requirements, and Roof Insulation

Today’s Pole Barn Guru answers reader questions about screw penetration into decking/substrate, header aka truss carrier requirements, and a proper roof insulation solution.

DEAR POLE BARN GURU: Should the screws for exposed fastener metal panel roofing COMPLETELY penetrate the 1/2″ plywood decking/substrate? STEVE in WARREN

DEAR STEVE: For through screws, they should not only completely penetrate any substrate, but also at least an inch into underlying purlins. Relying upon screws into decking only could prove to be a failure looking for a place to happen in a severe wind situation.

 

DEAR POLE BARN GURU: On a 14’ x20’ building with 4×6 post 8’ tall what are the requirements for the header beam or beams? Can I use two 2x10s one out and one inside? TIM in STATE ROAD

Ask The Pole Barn GuruDEAR TIM: Header beam (aka truss carrier) requirements can be determined by a Registered Professional Engineer and are based upon this formula:

(Roof live and dead loads) x (1/2 span of truss + any eave overhang in feet) x (column spacing in feet squared)

Divided by

8 x Sm (Section modulus of proposed beam) x Fb (Fiberstress in bending of proposed beam) x Cd (Duration of Load)

If resultant is less than 1, then beam is okay.

Here is an example, based upon assumption your building is in a minimal snow area, steel roofing over purlins, no or light weight ceiling) columns are every 10 feet, one foot overhangs and available lumber is 2×10 SYP #2

(20 psf + 10 psf) x (14’/2 + 1’) x 10’^2 / 8 x 21.3906 (Sm of a 2×10) x 800 x 1.15 = 0.15 <= 1

For sake of this example, a single 2×10 #2 SYP would be adequate in bending. It may not be adequate for meeting required bearing area (can be confirmed with truss manufacturer).

Beams and connections should also be verified for adequacy against uplift forces, as well as deflection.

 

DEAR POLE BARN GURU: I’m about to build my ‘Miracle Truss’ building which uses steel trusses with lumber purlins/girts. I have a concrete slab with 2″ Styrofoam and radiant heat to provide some warmth in the winter. I’m thinking of using foil/single bubble vapor barrier in between the roof sheeting and wood purlins. In the future I’d like to add bat insulation to the inside of the roof. For the walls I’m not sure if I should use a foil radiant film – non-permeable…or if I should instead use house wrap like ‘Tyvek’. Again, as time and $$ allows I’d like to add bat insulation and maybe OSB half way up the walls. I’d appreciate your professional opinion on how best to ‘wrap’ my building and also ‘future proof’ it in case I happen to win the lottery and can afford to fully insulate it someday. Thank you. RICK in HILLSBORO

DEAR RICK: Code will not allow you to place batt insulation between your purlins unless you have at least an inch of continuous airflow above from eave to ridge. Impossible to do given orientation of roof purlins.

I would use two inches of closed cell spray foam directly to underside of your roof steel. Later, you could fill balance of cavity between purlins with unfaced rock wool, or open cell spray foam. For your walls, use a Weather Resistant Barrier (aka house wrap) and you can add either Kraft faced batts or unfaced batts with a 6mil vapor barrier on the interior at a later date.

 

This entry was posted in Insulation, Pole Barn Questions, Pole Barn Design, Roofing Materials, Pole Barn Heating, Constructing a Pole Building, Pole Building How To Guides, Trusses, Ventilation, Professional Engineer and tagged , , , , , , on by .

Roof Insulation, a Riding Arena, and Closure Strips

Today’s Pole Barn Guru answers reader questions about insulating a roof to keep exposed trusses, the size limits for and equestrian riding arena, and whether or not to use closure strips between the gable (rake) trim and siding.

DEAR POLE BARN GURU: I have a 30×40 post frame building with cathedral style trusses. I really like the open look and don’t want to cover them with a ceiling. I want to insulate against the metal roof with vinyl faced blanket insulation to give a nice finished look. The roof currently has bubble wrap which I’m told I should remove so I don’t have two vapor barriers. Question is, if I remove the bubble wrap, is it ok to lay just blanket insulation between trusses or should I try to fill the 1.5″ space between purlins with foam board then blanket insulation over top of foam board. Or would filling the 1.5″ space with spray foam, then blanket over that? Thanks for any advice. BRIAN in LANDISVILLE

DEAR BRIAN: Only way to properly do as you propose is to remove bubble wrap, then have 2″ or more of closed cell spray foam insulation applied directly to underside of your steel roofing. Balance of insulation cavity can be filled with either more closed cell (best R value) or rock wool insulation (as it is impervious to moisture).

 

DEAR POLE BARN GURU: Need an open cover 150 L x 75 W x 13 H to function as a cover for an equestrian arena. Can a pole barn get this big? And if not what is the largest size we can go. JEFF in PINELLAS PARK

DEAR JEFF: While we have provided post frame riding arenas with up to 100 foot clearspans, in most geographical areas, wood truss fabricators are limited to building and shipping lengths up to 80 feet and overall truss heights of 12’.

Interior Clearspan Arena

For extended reading on riding arenas, please visit: https://www.hansenpolebuildings.com/2012/07/the-perfect-indoor-riding-arena/

 

DEAR POLE BARN GURU: Should I use closure strips between the gable trim (rake trim) and siding? The siding is tuff rib. STEVE in WARREN

DEAR STEVE: Standard form fitted closure strips are sized to only fit perfectly when applied at 90 degrees to length of steel panels. When going up rake trim, these closure no longer fit, however we have a perfect solution Emseal! https://www.hansenpolebuildings.com/2016/03/emseal-self-expanding-sealant-tape-closures/
To acquire, please reach out to Materials@HansenPoleBuildings.com along with lineal footage required and ship to zip code.

 

This entry was posted in Pole Barn Planning, Trusses, Ventilation, Insulation, Pole Barn Questions, Pole Barn Design, Horse Riding Arena, Roofing Materials, Pole Building How To Guides and tagged , , , , , , , on by .

Roof Insulation, Pole Barn Houses, and Adding Heat

Today the Pole Barn Guru tackles reader questions about the best method of insulating a building with no plans for a ceiling, planning a pole barn house, and adding heat to a completed post frame building.

DEAR POLE BARN GURU: I am insulating my 30×50 pole barn that is wrapped with Tyvek outside the purlins and I will use faced batt insulation on the 10ft walls. I will have it heated in the winter with the gable vents and cupola closed when working, but will not cool it in summer months. My question is what is the best method to insulate the roof as I don’t plan to add a ceiling? Currently, there is a radiant barrier on top of the roof purlins directly below the metal, and the only venting is the cupola and two gable vents. ERIK in FESTUS

DEAR ERIK: Without a ceiling I would have recommended two inches of closed cell spray foam applied directly to your roof steel – except you have a radiant reflective barrier in place (not a best thing to spray foam to). This method also means it would be nice and toasty between your trusses, but not so much in your working area.

Provided your roof trusses are capable of supporting weight of a steel liner panel ceiling, I would encourage you to consider it as an option, then blow fiberglass insulation in above liner panels. Alternatively, you could use lathe, wire mesh, or other means across bottom of trusses and place unfaced batt insulation on top.

 

DEAR POLE BARN GURU: I would like to know about building a pole barn house. 3 bed 1.5 to 2 bathroom. If I order from you do I build it of you? How much do they cost? DAVID in KALKASKA

DEAR DAVID: This article should get you started https://www.hansenpolebuildings.com/2021/02/a-shortlist-for-smooth-barndominium-sailing/

 

DEAR POLE BARN GURU: Heating an unvented barn? I have a 52×70 Hansen pole barn. I have decided I would like to heat the space. I have sealed the concrete and have spray foamed the walls with 2.5″ closed cell and blocked the soffit vents while doing this. I will be using a combo of a waste oil furnace and a wood stove to heat the space. My question is can I block off the gable vents instead of putting in a ceiling? Will I have moisture issues if I do this? I did use the foil insulation between the roof sheeting and the purlins that came with the package. Thanks. MARSHALL in CAMANO ISLAND

DEAR MARSHALL: Please keep in mind the Reflective Radiant Barrier under your roof steel is a thermal break designed to control condensation from occurring on underside of your roof steel, it is not insulation and has a R value of roughly one (R = 1). If you block off all vents, you may need to mechanically dehumidify your space in order to reduce moisture inside. Alternatively, should you install a ceiling and insulate above it, you would need to appropriately vent dead attic space to prevent roof system mold and mildew.

 

 

 

 

This entry was posted in Insulation, Pole Barn Homes, Pole Barn Questions, Roofing Materials, Barndominium, Pole Building How To Guides, Pole Barn Planning, Ventilation and tagged , , , , , on by .

Planning for a New Post Frame Home

When it comes to planning for a new post frame home, shouse or barndominium, there are a myriad of questions and concerns to be answered and pondered.

Or, at least I hope you are – rather than just stumbling in blindly!

Reader NICK in NORTH CAROLINA writes:

“Hi, I’m looking into options for building a post frame home in the coming year in NC and wanted to understand more of the details regarding you current building products and suggested techniques.  

Do you provide a means to support the posts on top of the concrete pillars with a bracket vs the post being embedded into the concrete?

Your current package only provides for insulation of the roof, no interior walls, correct?

Can another 2×6 skirt board be added to the inside of the building to isolate the concrete flooring from the post and to provide a cavity for insulation to be installed between the outside/inside girts?

Do you have a listing of contractors that are familiar with your products in given areas that could be used to build the structure?

If using the design service listed for $695, does that include the design for all interior walls/rooms/fixtures as well as electrical/plumbing/mechanical?

Thanks for any information you can provide.”

All good questions. In answer to them:

Yes we can provide plans with a third-party engineered design for bracket set columns, as well as brackets. https://www.hansenpolebuildings.com/2019/05/sturdi-wall-plus-concrete-brackets/

We typically recommend using either a Reflective Radiant Barrier (https://www.hansenpolebuildings.com/2017/05/effective-reflective-insulation/) between roof framing and roof steel, or using roof steel with factory applied Dripstop https://www.hansenpolebuildings.com/2012/11/drip-stop/

We can provide batt insulation for walls and/or ceilings, however there are more energy efficient methods of insulating https://www.hansenpolebuildings.com/2018/06/pole-barn-insulation-oh-so-confusing/

It (extra 2×6 interior splash plank) could, however there are structural advantages to having columns surrounded (constrained) on exterior splash plank interior. (https://www.hansenpolebuildings.com/2018/11/importance-of-constrained-posts/) I’d recommend doing a Frost Protected Shallow Foundation post frame style instead: https://www.hansenpolebuildings.com/2017/09/post-frame-frost-walls/

About Hansen BuildingsAlthough our buildings are designed for an average literate English speaking person to successfully construct their own building (most of them do, and do a wonderful job – because they will read and follow instructions), for those who do need an erector, in many areas we can provide contacts for you to vet.

Our floor plan and elevation package offer (http://www.hansenpolebuildings.com/post-frame-floor-plans/?fbclid=IwAR2ta5IFSxrltv5eAyBVmg-JUsoPfy9hbWtP86svOTPfG1q5pGmfhA7yd5Q)  includes all interior walls, rooms and fixtures. For an added fee you can include electrical/plumbing/mechanical (note: typically all of these last three services can usually be provided at no charge by subcontractors who will be doing these specific trades).

Please feel free to reach out to me at any time with questions. An answer to most questions can also be found at www.HansenPoleBuildings.com by clicking on SEARCH in the upper right hand corner of any page. Type in a word or two and hit ENTER and up pops relevant articles.

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When the Pole Building Insulation Problem is Larger Than Imagined

When the Pole Building Insulation Problem is Larger Than Imagined

From questions I have received from loyal readers over the past year, post frame (pole) building insulation is right there at the top of the list for priorities. Sadly, it seems the same concern is not often put forward by those who are designing, providing and constructing post frame buildings – leaving far too many new building owners in a world of hurt.

DISCLAIMER: This is NOT a Hansen Pole Building

Reader KEVIN in WEST CHESTER writes: “When installing my insulation do I stop just short of the vented soffit inside at the top of the wall?”

Well, this is an easy question to answer – the wall insulation needs to not cover the air intake provided from the eave vents, if the thought is for them to be used as a functional vent.

Simple, wasn’t it?

Now we can get into the challenges presented in the photo.

Unless the walls are going to be insulated with closed cell spray foam, there should be a well-sealed building wrap between the wall framing and the wall steel. This allows any moisture which would be trapped in the wall to be able to pass through to the outside world.

Now, onto the big challenge – insulating the roof.

If the idea is to have the vents in the low eave soffit be an air intake, then there needs to be a corresponding air exhaust at the high end of the shed. Along with this there needs to be the ability of unobstructed airflow from the low eave to the high side above the roof insulation. This happens to be a Building Code requirement, not to mention it is designed to prevent mold, mildew and other associated decay issues. As the roof purlins appear to be an impediment to airflow if the cavity is filled – the solution may end up being to have to use closed cell spray insulation under the roof sheathing and do away with the eave ventilation.

Moral of the story – consider insulation and ventilation needs early on in the project, in the planning stages, not after the building shell is already constructed.

This entry was posted in Ventilation, Insulation, Pole Barn Questions, Pole Barn Design, Building Overhangs, Pole Barn Planning and tagged , , , , on by .

Should Poly Plastic Barrier be Used on Interior of Walls and Ceiling?

Reader JUSTIN in MONROE writes: “Hello. Hopefully an easily answered question? I have built a 52×30 post frame, steel siding and roof. Walls have Tyvek between steel and girts. Roof is steel directly on purlins with no barrier of any kind. It has a concrete slab and I plan to periodically heat it during winter months. I’d like to insulate but not sure of best method with my situation and climate. I plan to use R-19 for walls and possibly ceiling. Or blow in for ceiling. Also I have 50% soffit ventilation with 18″ overhang as well as 40 ft of ridge vent. Should I use poly plastic on interior of walls and ceiling? I’m concerned I will create a moisture problem. I’m open to doing things whichever way is best. Things are always easier and cheaper to do it correctly the first time. Any advice would be greatly appreciated. Thanks”

Dear Justin,

housewrapI agree things are always best when done correctly the first time around. While it is not always less of an investment, when the long term problems arise and things have to be corrected, it makes it nearly not as fun and cheap becomes expensive. Usually in a quick hurry.

If the roof trusses are not designed for at least a five pounds per square foot bottom chord dead load, you are sunk on adding a ceiling without an engineered truss repair. This would be the place to start, as it will dictate the solution.

I will approach the building as if it is my own and from where it is now.

On the floor – I am hoping you have a vapor barrier beneath the concrete slab. If not, use a high quality sealer on top of the floor.

A penetrating concrete floor sealer is likely the best bet to protect and maintain a concrete floor. These concrete floor sealers penetrate deep into the concrete’s pores coming into contact with the alkali and calcium ions, forming a gel.

This gel expands filling the pores and hairline cracks inside the concrete, turning the concrete into a solid mass. This process will prevent moisture and vapor migration up through the concrete floor, as well as down into it.

Look for a penetrating concrete floor sealer which is water based and says silicate penetrating solution on the specifications. These sealers can be applied with a pump up sprayer.

On the Walls-you did good with the Tyvek. Kudos! If your building has girts flat on the outside of the columns, you can add another set to the inside of the columns. If you have 6×6 columns, your post frame building will now have an 8.5 inches thick insulation cavity. I would use BIBs (read about BIBs here: https://www.hansenpolebuildings.com/2011/11/bibs/) for my wall insulation, and would have a deep enough cavity to get around R-35. There does need to be a vapor barrier on the inside (heated) side of the wall, under the gypsum wallboard.

Roof– the underside of the roof steel needs to be isolated from any warm moist air which would enter the attic. Use closed cell spray foam directly sprayed directly onto the underside of the roof steel. Assuming your building’s roof trusses are strong enough to support a ceiling, blown in insulation is going to be your most economical. Hopefully you (or your builder) had the foresight to order roof trusses with a raised heel so the insulation will remain full thickness from wall to wall. If not you may want to have closed cell spray foam insulation on the “cold” side of the ceiling in the area with a couple of feet from the sidewalls. Make sure to allow a provision for air in the overhangs to not be blocked from venting the attic.

Do not put a vapor barrier between the trusses and the ceiling. You want the warm moist air inside your building to be able to rise into the attic and be vented out through the ridge. And if you are going to insulate your ceiling, R-19 is really not near enough. At a minimum I’d think about R-38 or 45 blown in.

Thank you for allowing me to share some insight into insulation.

Mike the Pole Barn Guru

This entry was posted in Insulation, Pole Building How To Guides, Ventilation, Building Interior and tagged , , , , on by .

Insulation Between Roof Purlins

From the number of “Ask the Pole Barn Guru Questions” I receive and the new pole buildings I see being constructed, climate control is of very high importance. When I first entered the post frame industry 35 years ago, no one cared about it as virtually all ‘pole barns’ were farm buildings or small private garages. Not the case anymore! Pole Buildings run the gamut from heated shops, airplane hangers with living spaces and custom designed homes or year around lake cabins.

For heating and cooling, it is most efficient to have to control the least amount of space. Reducing the height of the area to be heated, will result in more comfortable temperatures in the area humans typically occupy.

Installing a ceilingThis area can be reduced by finishing off the ceiling (with my personal preference being gypsum wallboard) and blowing in insulation above the ceiling – along with having a properly ventilated attic space. To give a rough idea of the volume of space differentials on a 40 foot wide by 60 foot long by 12 eave height building, having the most typical roof slope (4/12), about 25,000 finished cubic foot of area is to be conditioned with the ceiling, as opposed to nearly 34,000 cubic feet otherwise.

A significant amount of some sort of fuel is going to be used to heat or cool the extra one-third volume of space!

Some people prefer to insulate between the building roof purlins, however this can be fraught with potential challenges if not done properly.

The easiest solution, however possibly not most cost effective, is to utilize spray foam insulation. For most people, this is just not an affordable solution (read more at: https://www.hansenpolebuildings.com/2014/02/insulation-foam-fiberglass/).

Unfaced (typically fiberglass) insulation can be placed between the purlins. The purlin dimensions can be increased to allow for thicker insulation – which will be required (in most cases) if energy code requirements need to be met. By Code, airflow must be provided above this type of insulation. As roof purlins run the longitudinal direction of the building, 2×4 material can be placed flat on top of the purlins, running from eave to ridge. In order to utilize the space created by these 2x4s, the eaves and ridge will need to be ventilated.

A vapor barrier will need to be installed above the air flow area, if the roof is through screwed steel over purlins. An ideal solution would be a reflective radiant barrier, with another flatwise layer of 2x4s placed on top of it (in the same direction as the roof purlins). This creates another dead air space which improves the efficiency of the reflective radiant barrier.

Seriously looking to insulate between roof purlins while conserving energy? Design it right in the beginning!

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Attic Insulation Guide

Pole Barn Guru BlogWelcome to Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays.  With many questions to answer, please be patient to watch for yours to come up on a future Monday segment.  If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU: I am building a 24’x32′ pole barn type shop using 5 clerestory trusses in which I will install windows in the verticals for natural light. I want the roof shingled and insulated. Is there a way to frame in roof rafters between the trusses to carry the weight of the roof sheathing and to use batt insulation underneath? SCOTT IN ELLERSLIE

DEAR SCOTT: For sake of discussion, we will assume the trusses have been engineered to carry the weight of all of the materials you will be adding.

In order to use batt insulation as you propose, Code requires there to be at least a one inch air space between the top of the insulation (which must be unfaced) and the underside of the roof sheathing. This space must be vented at eaves and peak, and airflow must not be impeded.

Just off the top of my head (and knowing nothing about how your trusses are constructed), I’d probably look at placing a header at the eave and peak, which would carry 2×12 rafters placed every 24 inches and running the same direction as the trusses. Insulation batts up to 10-1/4 inches thick could then be placed between the rafters.

You should consult with the RDP (Registered Design Professional – architect or engineer) who designed your building, to confirm sizes and connections of members, as well as their adequacy to carry the imposed loads.

Mike the Pole Barn Guru

DEAR POLE BARN GURU: My name is Ben, and my husband and I plan to build a timber pole house in the mountains around Luray, VA. We are still in the planning stages, but are already working on the design stage of the house. I wanted to reach out and see if you offer the type of services we need, even though your website seems like you would be just perfect.

As a quick summary of our needs:

I am a 3d artist and am laying out the space in 3ds max to get an idea for room size, arrangement, and other proportions. However since I am not an architect, I need someone to go over the design, make it useable, point out any problem areas I am unaware of as a non-architect. Also being able to get all the materials cut and shipped to our building site is a huge plus.

Additionally, as we are still researching land, I would like input on what to look for based on our design, and then after land is procured, any adaptations needed for our plan to fit the space (the biggest thing I am worried about, is pile depth for the timber piles to pass code and be structurally sound). We plan on a 2 story building, so it’s likely the max timber height above ground would be around 35 feet for some of the timbers. We also plan to build on a mountain side, so the timber length would vary.

Is this the kind of service you can offer?

Thanks so much for your time,  BEN AND AGUST IN LURAY

DEAR BEN: We can supply columns up to 60′ in length, so you should not have any difficulties with what you have in mind – nor will needing various lengths be a challenge.

Our designs do not incorporate interior non-load bearing walls, as we have found room sizes tend to change greatly once the exterior shell is up and clients get a much better feel for what each room will do, as well as for orientation. Always try to work from the inside out – determine (at least close to) the area of the spaces you will need and then orient these spaces to be most functional for your lifestyle. Then create an envelope which fits around your spaces.

The ultimate location may (and should) play a great deal into the final design. Orientations should be such to take advantage of the most practical approaches to the site, as well as views and exterior living spaces (decks and patios).

Keep in mind – any pricing done now, is based upon where markets are at today. Lumber and steel are commodity items and prone to a great deal of variability which is beyond anyone’s control. Allow plenty of safety cushion in your budget, it is always a pleasant feeling to have more money left over, than having to scramble because things were planned too tight.

Mike the Pole Barn Guru

DEAR POLE BARN GURU: I am interested in pricing for a pole barn/apartment.  I am selling my house and will be purchasing roughly 15 acres of land.  I would like a pole barn constructed on the land.  I intend on building my own home which will take some time.  I would like a two story pole barn, with the upstairs being the finished apartment with somewhere around 900 square feet so I can live on my property while my house is being built.  Is this something that you would be able to do?  Thanks for your time. JEFF IN CINCINNATI

DEAR JEFF: Thank you very much for your interest in a new Hansen Pole Building. We provide post frame (pole barn) building kit packages similar to what you have in mind on a regular basis. You will be contacted shortly by one of our Building Designers to get more detailed information as to your exact needs.

Mike the Pole Barn Guru

This entry was posted in Insulation, Pole Barn Questions and tagged , , , , on by .

Insulation for Box Beams

What I get to do every day is nothing short of fun. My life is full of interesting questions from many different angles. Today’s opportunity is compliments of Hansen Pole Buildings Designer Rachel who writes, “Guy called asking on the vapor barrier.  I know we have discussed this before but I want to make sure to tell him correctly.

He has a barn with box beams,  basically 2×12 box beams with 2×6 purlins running in between.  There is no vapor barrier under the steel and he would like to insulate with fiberglass insulation.  So would you recommend cutting and putting a vapor barrier up against the steel and then insulation or what is the RIGHT way to do this.  He has conflicted answers from people he has asked. 

FYI…he can’t put in a flat ceiling.  Also he has vented soffits but no ridge vent.”

From the description it appears instead of trusses, this particular building has some combination of 2×12 built up box beams or rafters, supporting purlins on edge in between.

The building has been constructed omitting one of the most crucial elements – a thermal break between the roof framing and the roof steel. I am at a loss to come up with an answer as to why so many steel roofs do not have some method of controlling condensation.

Given what information I have, here are some solutions:

Spray Foam InsulationIf the client wants to add some actual R value to the solution – then spray foam is going to be the way to go. Yes, it is costly, but the other alternatives are not pretty as well.

If he is looking to only control condensation – remove the roof steel, install an insulated vapor barrier as a thermal break (such as a reflective radiant barrier available at www.buyreflectiveinsulation.com) and reinstall the steel, using larger diameter and longer screws than what were originally used.

At the same time, a continuous ridge vent should be installed.

In order to use a vapor barrier and gain actual R value (such as insulating between the purlins), the Building Code requires there to be airflow above the insulation, which would entail a rework of the roof framing (besides removal and reinstallation of the roof metal). And this choice would definitely require work and expense.

Back to my first suggestion – for time and money to accomplish the goal – use spray foam insulation underneath the box beams and roof steel.

This entry was posted in Insulation and tagged , , , on by .

Insulation: Foam It or Fiberglass It?

I enjoy Hansen Pole Buildings’ Designers who really like to sink their teeth into a subject.

This morning Rick asks me, “Have you ever done a cost comparison on spray foam roof insulation vs the costs of condensation barrier, ceiling load trusses, joists, drywall ceiling and blown in insulation?”

The entire question was brought about, as Rick really gets his clients to think about how they will be using their buildings.

In order to do a comparison, I just plucked from the air a 40’x60’ building, double trusses every 12’ with a 4/12 roof slope and 12” overhangs. Fairly common, pretty standard.

So, what needs to be done in order to spray foam a pole building?

Spray Foam InsulationFor starters, keep in mind (by Code) spray foam insulation cannot be left exposed, it has to be covered with inflammable material – like gypsum wallboard. Gypsum Wallboard is not as flexible as steel, so it has deflection criteria which mean upsizing the roof purlins from 2×6 to 2×8, or changing the column spacing to 10’ on center(o.c.). In the end, when I priced it out the change to 10’ o.c. was less costly, adding only about $900.

In either case, the truss loading will need to be increased to support the extra weight of the system – the top chord loading for spray foam or the bottom chord to create the dead attic space. Statistically – pretty much a wash in costs.

Due to the run of the roof, the spray version is going to take a little more drywall – call it $50

In the northern ½ of the United States, the recommended minimum attic insulation is R-49.

Spray foam is not inexpensive. With 2×6 purlins on edge, the maximum foam insulation thickness is 5-1/2 inches. At R-7 per inch for closed cell foam, will result in an R 38.5. The going rate for spray foam runs from $1 to $1.25 per square foot (sft), per inch of thickness – plus travel and fuel surcharges. To keep it easy, I will use $1 and ignore the rest. Including the run of the roof, roughly 2520 sft at $5.50 per sft is going to cost $13,860.

Total added costs for spray foam = $14,810

How about fiberglass in a dead attic space?

Increased truss load has previously been covered.

Ceiling framing must be added between trusses to support the wallboard – roughly $1200 including all of the Simpson hangers.

A reflective radiant barrier must be placed between the roof purlins and the roof steel, to prevent condensation, which would then rain on the insulation. $650

And the ridge must be vented. Under $200

According to Lowe’s, to get an R49 with fiberglass would require 74 bags of blow-in insulation at $32.75 a bag for just over $2400.

Total costs for fiberglass = $4450.

In summary, spray foam costs would be roughly 333% of the cost of fiberglass, to get to 78% of the R value. The other downside is with spray foam, the area of the trusses now has to be heated (almost 8000 cubic feet of space) before the area below it is going to feel warm!

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How To Add Insulation Between Purlins

If you happen to be considering building a pole building in a part of the country where sidewall columns MUST (it is a mindset, not a structural requirement) be every eight feet and trusses MUST be every two or four feet, then it is time to take a leap of faith out of the very small box!

Read more on truss spacing here: https://www.hansenpolebuildings.com/blog/2011/06/pole-barn-truss-spacing/

On to the topic at hand…..

insulation roll

Whilst I am a proponent of insulating above flat level ceilings, there are cases where this just isn’t what people have in mind for their new post frame buildings. Whether it is to create dramatic vaulted ceilings, or just to be different, every reason is valid.

The challenge is… how to get adequate insulation between purlins into a typically very small area.

With typical “Western” style pole barns, double trusses are placed every 10 to 14 feet with 2×6 or larger roof purlins on edge between the trusses.

Even using high density insulation batts, the R-23 from a 2×6 insulation cavity is only going to be adequate in the deepest South.Ceiling R Values

There ARE solutions….using larger roof purlins being a very simple one. Using high density batts would allow for R-46 in a 2×12 purlin. Or, for increased depth, furring strips could be added to the underside of any sized purlins.

If gypsum wallboard is to be added to the underside of the roof purlins, a deeper purlin is often required to prevent undue deflection from cracking drywall joints.

Oh, I forgot to mention, purlins are best placed 24 inches on center, to fit with the most common insulation width, and insulation between purlins should be unfaced.

Further insulation may be added by the use of high R foam boards placed beneath the purlins; however Code requires them to be covered with a fire barrier on the inhabited side.

For more foam board information: https://www.hansenpolebuildings.com/blog/2012/04/rigid-insulation-boards/ and https://www.hansenpolebuildings.com/blog/2012/04/foam-board/

There IS a challenge, which we have not yet delved into….ventilation is required between the insulation and the roof deck. The roof purlins running the length of the building prohibit airflow, and even if the insulation was not the same thickness as the cavity (depth of the purlin), not enough holes could be drilled through the purlins to allow adequate airflow and not degrade the purlin strength.

The solution: Lay 2x4s flat on top of the purlin, running up the roof. Although these 2×4’s and their connections need to be structurally verified against uplift conditions, in most cases, spaced every four feet will prove adequate. This space will become the “air chase” between vented sidewall overhangs and the vented ridge cap.

On top of this layer of 2×4’s, reflective radiant barriers needs to be placed.  This prevents warm moist air from contacting the underside of the roof steel. Using a product with a tab along one edge with an adhesive pull strip, helps to make sure no air will leak through the vapor barrier. (Go to www.buyreflectiveinsulation.com for reflective radiant barrier information and pricing).

In order to attach the roof steel, yet another layer of flat 2×4 needs to be added. As the previous layer runs from eave to ridge, this layer will be used to attach the roof steel. Spacing of these will be dependent upon the snow and wind loads, but they usually will be no greater than 32 inches on center. Besides affording the ability to attach the purlins to a wide target (the 3-1/2 inch face of the 2×4), the dead air space increases the effectiveness of the reflective radiant barrier.

This entry was posted in Insulation and tagged , , on by .

Drip Stop

When the temperature and humidity conditions reach the dew point, moisture can condense on the underside of steel roofing. This condensation has the potential to cause water damage and other problems inside of pole buildings.

Some of the Hansen Pole Buildings steel suppliers are now offering an internationally patented CCM (Condensation Control Membrane) which can be pre-applied to their steel panels. This innovative product works by creating a medium for trapping moisture in the specially designed pockets formed within the felt’s membrane. Holding moisture until conditions go back below the dew point, Drip Stop is then able to release the moisture back into the air in the form of normal humidity.

Drip Stop is durable – it isn’t susceptible to ripping, tearing or deterioration like many common metal building insulation and vapor barrier products. It is easily cleaned with a hose or pressure washer. It may result in time savings – as no other product needs to be installed between the roof purlins and roof steel. It is approved for use in animal confinement buildings. Drip Stop is UL 723 approved for flame spread and smoke generation and comes with a 20 year adhesion warranty. It also reduces exterior noise.

The skids of steel with Drip Stop applied must be stored prior to use, to prevent moisture from becoming trapped between panels, which may cause staining as well as damage to the panels. This moisture can originate from a variety of sources, such as rain, high humidity or condensation. Panels should be stored in a dry location and installed as quickly as possible after delivery. If this is not possible, panels should be separated from one another to allow for air circulation to prevent panel damage.

The steel panels do require some extra preparation work, prior to installation. Panels are to be first laid with the Drip Stop material facing up. Using a heat gun, the exposed end lap or eave portion needs to be heated to fuse the Drip Stop fibers. Care must be given to avoid overheating any one spot, which could potentially damage the panel’s finish on the exterior side. The Drip Stop material should neither be completely melted, nor fused beyond the lap or overhang area of the panel. Allow panels to cool, prior to installation. Failure to properly prepare panels may result in the Drip Stop material attracting water from outside the building, resulting in possible leaks, mold and/or mildew.

If anyone has personal experience using this product, feel free to respond and let me know what the pluses and minuses were in using Drip Stop.  It sounds like a great product, and may be a step in the right direction for a better moisture barrier than what has been currently available.  However, at first glance the application sounds too complicated and somewhat risky for anyone other than someone who has lots of practice installing it. Let me know what you think folks,  I am always looking “for a better mousetrap”!

This entry was posted in Roofing Materials, Steel Roofing & Siding and tagged , , on by .

Insulation Dilemma

A reader writes (spelling, grammar errors included):

“When I built my barn I had 2″ insulation bats put between the outside framing and the tin. The side toward the tin is just open insulation. The inside is that heavy with plastic or whatever it is. I built with books shelve perlins on 2′ centers. Thinking it would make it an easy job to just fill those cavities with insulation. 

Where I’m confused is on the vapor barrier. We have a local business that makes insulation. Actually my insulation came from them. They guy there told me to just slice open the white vapor barrier and add insulation then use plastic over the added insulation prior to finishing my walls. So I’m just looking for affirmation that this is the correct way to go. Or other ideas and opinions.

Thanks.”

From the description, I will assume the two inch insulation batts are what is known as Metal Building Insulation. This type of insulation is actually designed to reduce condensation issues in building which have steel roofing and/or siding applied directly over roof purlins or wall girts.

Metal Building Insulation is not an effective insulator, as the fiberglass insulation gets crushed down to nothing every time it crosses a framing member.

This particular building is designed with sidewall framing (girts actually, not purlins which are on a roof) placed bookshelf style to create an insulation cavity. The builder did not do his customer any favors and actually spent his customer’s money unwisely.

Moisture within the walls of a pole building can cause serious problems.  In the colder months, moisture tends to move from the inside to the outside of buildings.  As it passes through the walls, it may condense within them, causing the potential for rot and mildew.  In walls with insulation, the water may condense within the insulation decreasing its R-value.  In the worst case, moisture can actually freeze within the walls, accumulating until a thaw melts it and causes visible damage such as wall or ceiling staining!

A vapor barrier is designed to keep moisture in pole barns from getting inside exterior walls.  Batt and roll insulations usually come with a vapor barrier attached.  However, leakage can occur where the facings meet.  This is especially true if the facings are not stapled to the inside of the wall girts, but instead the insulation is just pressed into place or stapled on the inside of the girt (all too common of a practice with foil faced insulation).  For the best possible vapor barrier, supplement the facing by installing a 4mil or thicker clear plastic sheet over the inside of the entire framed wall before installing any interior finishes (like gypsum wallboard).

Never sandwich the insulation between two vapor barriers. For example, do not install insulation with the vapor barrier facing the climate controlled space and then put plastic sheeting, or some type of vapor barrier, across the outside of the framing. Since some leakage of moisture into the insulation in inevitable, it needs to be able to freely escape from the insulation to the outside world ….. not be trapped inside!

 

This entry was posted in Pole Barn Planning, Pole Barn Structure, Steel Roofing & Siding and tagged , , , on by .

Cool Roofs

I’m not talking about roofs that look “cool”. Cool roofs are the roofs which deliver both high solar reflectance and thermal emittance. Solar reflectance is the ability to reflect the visible, infrared and ultraviolet wave lengths of the sun, reducing heat transfer to the building. Thermal emittance is the ability to radiate absorbed, or non-reflected solar energy.

The benefits associated with cool roofs include reduced cooling energy load, reduced air pollution and improved human health and comfort. Cool roofs may extend the roof service life. They achieve cooling energy savings in hot summers but can increase heating energy load during cold winters.As such, the net energy saving of cool roofs varies depending on climate. Without a proper maintenance program to keep the roof material clean, the energy savings of cool roofs can diminish over time.

While it is true cool roofs are mostly associated with white roofs, they come in a variety of colors and materials and are available for pole buildings of all uses. Today’s “cool roof” pigments allow metal roofing products to be Energy Star rated in dark colors, even black. They aren’t as reflective as whites or light colors, but can still save energy over other paints.

Most of the roofs in the world (including over 90% of the roofs in the United States) are dark colored. In the heat of the full sun, the surface of a black roof can increase in temperature as much as 125 °F, reaching temperatures of 190 °F. This heat increase can cause negative effects on cooling energy use.

Cool roofs, on the other hand, offer both immediate and long-term benefits: Reduced building heat-gain, as a white or reflective roof typically increases only 10–25 °F above ambient temperature during the day; Savings of up to 15% on annual air-conditioning energy use for a single-story building; Extended service life of roofs; Improved energy efficiency of roofs, especially when there isn’t adequate insulation provided in the roof envelope; and Improved thermal comfort in buildings which do not have air conditioning.

Research and practical experience with the degradation of roofing materials over a number of years have shown heat from the sun is one of the most potent factors which affect durability. High temperatures and large variations; seasonally or daily, at the roofing level are detrimental to the longevity of roofing. Reducing the extremes of temperature change will reduce the incidence of roofing damage. White surfaces reflect more than half of the radiation which reaches them, while black surfaces absorb almost all. White roofing would appear to be the best approach to control problems where roofing is exposed to solar radiation.

In some climates where there are more heating days than cooling days, white reflective roofs may not be effective in terms of energy efficiency or savings because the savings on cooling energy use can be outweighed by heating penalties during winter. According to the U.S. Energy Information Administration, 2003 Commercial Buildings Energy Consumption Survey, heating accounts for 36% of commercial buildings’ annual energy consumption, while air conditioning only accounts for 8% in United States. 

According to the Cool Roofs Rating Council and other sources, “The roof is an insignificant source for heat gain in winter. While cool roof owners may pay slightly more to heat their pole buildings, this amount is usually insignificant compared to the cooling energy savings during the summer”. Energy calculators generally show a yearly net savings for dark-colored roof systems in cool climates. The energy trade-off is therefore not clear cut. Additionally, higher R values for insulating materials in the roof assembly and snow covering on roofs can lessen the impact of roof surface color.

Choosing a roof which is not only “cool looking” but functions as a cool roof, is the way to go!

This entry was posted in Roofing Materials, Pole Barn Planning, Steel Roofing & Siding and tagged , , on by .
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