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What Size Fresh Air Intakes Do I Need?

What Size Fresh Air Intakes Do I Need?

Reader BOB in GRAHAM writes: “I have a 40 x 60 pole building. There is a ridge vent along the 60′. I recently installed Sheetrock on the ceiling and blew in insulation. My question is what size fresh air intake vents do they need to keep the attic cooler. I was thinking I need Air vents on each side of the end wall at the lowest points. The other thing is I can only pull fresh air in at one end of the building. As the other end is open to the ridge vent, separate from the other 60′. Should I put an electric intake fan rather than just an air vent?”

Here are ventilation requirements:

Provision of 1 square foot of NFVA (Net Free Ventilation Area) for each 150 square feet of attic floor. One important note – attic floor area is just as it reads – area – not volume. This is a minimum requirement and does not stipulate required ventilation openings provide intake (low), exhaust (high), or both.

Provision of 1 square foot of NFVA for each 300 square feet of attic floor if both following conditions are applicable:

At least 40%, but not more than 50% of NFVA is provided by vents located not more than 3 feet below roof’s highest point.

Provision for a minimum 1 inch air space between roof sheathing and insulation in attic at vent location.

Your 40 x 60 building would therefore require at least eight square feet ( 40 x 60 = 2400 / 300 ) or 1152 square inches of NFVA, with at least 50% of this been at eaves (vented sidewall soffits) or gable vents located in lower half of attic space.

While an electric powered fan would move air within your attic area, you do need to provide adequate intake area. 576 square inches of NFVA is a lot of gable vent (assuming you have no soffit intake vents).

This entry was posted in Roofing Materials, Constructing a Pole Building, Ventilation, Building Interior, Pole Barn Heating, Insulation, Pole Barn Questions and tagged , , , , , , on by .

Insulating an Existing Pole Barn

Insulating an Existing Pole Barn When Things Started Wrong

Reader TOM writes:

“Mike,  I have an existing pole barn (6×6 post with 2’ on center girts ) that has a 4” concrete floor with 10 mil plastic under it. The side walls have 1” XPS insulation on the outside of girt then steel siding with no wrap or barrier. My thought is put Tyvek on inside of girt ( facing same direction as if on outside application ) then put inch and a half XPS DOW insulation against that ( because there’s two bunks already there) then 2×4 frame with batten insulation between them, then 6mil or heavier vapor barrier then OSB. The floor has PEX tubing in it but not hooked up. Is this a proper install?  Also I will have to have an engineer check the BCDL as I want to put OSB on the ceiling but would like to know how to insulate the ceiling. There is a one foot fully vented overhang with a ridge vent also. Thank You for the info in advance. 

Mike the Pole Barn Guru advises:

I am concerned about your building having an inch of XPS insulation between girts and siding. This allows screw shanks to flex, potentially creating slotting under screw heads and excessive deformation can result in your building cladding’s shear strength being compromised and (under extreme circumstances) racking enough to create a failure. I would feel much more comfortable if you were to add 7/16″ OSB or 1/2″ CDX plywood to the inside of girts in bays on each side of corner columns from splash plank to eave girt.

Moving forward….

Your external XPS is now acting as a vapor barrier (or close to it). Any exposed to inside seams should be taped. Do not put Tyvek on the inside of the girts, as this would allow any moisture in assembly to be trapped between it and XPS. Unless you already own a pile of 1-1/2″ Dow insulation, skip it and instead fill the balance of the wall cavity with rock wool or stone wool unfaced batts. Do not place a vapor barrier on the inside or seal OSB on the inside of the wall. Walls will now ‘dry’ to inside.

Provided your trusses are capable of supporting a ceiling, blow in fiberglass above your ceiling finish of choice. Make sure to allow at least an inch of air space above insulation at eaves so you get proper air intake from vented soffits. Unless you are very close to Canada and have at least 8000 heating degree days, do not add a vapor barrier at ceiling level.

This entry was posted in Insulation, Pole Barn Questions, Building Overhangs, Pole Building How To Guides, Pole Barn Structure and tagged , , , , , , , , , , , on by .

Being a Fan Fan

Being a Fan Fan

Reader TOM in MACOMB writes:

“Hello, I have a 24 x 40  pole barn built last summer. It has a base layer of 10” of sand and 4’ of crushed concrete on top. This sat exposed for several months until the building was erected,it was a wet summer. The building was finished in August and has a thin vapor barrier under the metal roof. As soon as the nights started turning cool moisture started dripping from the ceiling, especially from the 3 crystal panels. This building does have a gutter with good drainage. The moisture is coming from the ground as any plastic set on the ground overnight will result in heavy condensation underneath. So with that said I am hoping this issue is simply leftover moisture that will eventually dry up in time. However mold is developing and things are rusting. I would like to speed up or help the moisture leave the building. It does have soffit vents and ridge vent. Finally to my question. Can I put in an exhaust fan or a giant ceiling fan or both to help this process? I wasn’t sure which may be better, power vent on the roof or in the gable would be better. Or perhaps a 96” ceiling fan would be enough to push air through the ridge vent. Although the vent is covered with snow in the winter as this is in northern Michigan. Thanks in advance for any advice.”


Mike the Pole Barn Guru

My educated guess is your building’s concrete slab on grade does not have a well sealed vapor barrier underneath. If this is indeed true, you need to start by removal (or minimization) of your moisture source – put a good sealant on your slab’s surface.  There are other things to be done once ground thaws, we will get to them in a moment.

A powered gable exhaust fan will help to get moist air out from inside your building. Whether your proposed exhaust fan will be adequate or not will be dependent upon its CFM (cubic feet per minute) capabilities. You will probably want to plan for around 10 air exchanges per hour. If you have a 14 foot high ceiling, then 24 x 40 x 14 = 13,440 cubic feet (plus area above eave height at 4/12 slope is another 1920 cubic feet) X 10 times / 60 minutes per hour = 2560 CFM.

Come Spring – grade away from your building at least 10 feet at a 5% or greater slope. Make sure all downspouts discharge outside of this graded area. You may find it necessary to install a French Drain around your building’s perimeter in order to keep groundwater from running under your building.

This entry was posted in Building Overhangs, Constructing a Pole Building, Pole Building How To Guides, Ventilation, Concrete, Building Drainage, Building Interior, Pole Barn Questions and tagged , , , , , on by .

My Barndominium Attic Has Moisture Issues!

My Barndominium Attic Has Moisture Issues!

Reader DAVID in CHICAGO writes:

“Greetings – I’ve got a pole barn style home that’s about 2.5 years old and I’m having moisture issues in the attic. Hoping I can talk with someone to get a consult or second opinion to resolve as quickly as possible. Let me know if it is something you can connect on. Attached is an image from the attic where you can see moisture on the underside of the metal roof. It freezes at night and then during the day when the sun is out, it melts and drips into the attic insulation. 

Attic space is dead, image below. Vented through passive soffit vents and ridge vent, with a few solar blaster ridge vents to help with active venting when the sun is out. Attic insulation is R50 blown in at 20 inches deep. Image of exterior attached. It’s sheet metal that’s then spray foamed on the inside and additional R25 batts. Image below from when we had this same issue earlier this year in February 2021 when the drywall walls and ceilings had to be torn out due to water damage. We purchase in January 2021 and the home is now 2.5-3 years old. There is a solid concrete slab that has in-floor heat. I believe it has a vapor barrier underneath from an image I saw. “

Mike the Pole Barn Guru writes:
You are victim of what is such a simple and economical solution, when planned for in advance. Why builders and building providers fail to address steel roof condensation initially drives me to consider alcoholism!

I do realize they are just ‘selling on a cheap price’, rather than providing a best solution for their client.

Easiest solve is to have two inches of closed cell spray foam applied to underside of roof purlins. Any other solutions will take removal of roof steel panels, adding a thermal break, and then reinstalling roofing.

At time of construction I would have recommended roof steel with an Integral Condensation Control (ICC) factory applied. Investment then would have been a fraction of having to solve it now.

For extended reading on ICCs https://www.hansenpolebuildings.com/2020/09/integral-condensation-control-2/.

This entry was posted in Pole Barn Homes, Insulation, Post Frame Home, Pole Barn Questions, Pole Barn Planning, Barndominium, Shouse, Ventilation and tagged , , , , , , , on by .

Condensation Issues, Adding a Loft, and Metal Truss Load

This week the Pole Barn Guru discusses issues with condensation in a new building, advice for adding a loft, and achieving a roof load for prefabricated metal trusses.

DEAR POLE BARN GURU: Hello, I have a new construction pole barn that I recently had put up. The building is used to primarily house animals. When I had it put up I was told I would have to condensation issues with eave vents and a ridge vent that would extend the whole length of the building. The dripping really bothers me and I was wondering if there is a good option of putting a barrier of some sort on the bottom side of the purlins? My rafter spacing is 8ft. THOMAS in NEW SALEM

DEAR THOMAS: In most instances eave and ridge vents are inadequate alone to prevent condensation. Contractors who fail to include some sort of thermal break between roof framing and roof steel are doing a severe disservice, in my opinion. It is so easy to accomplish at time of construction with products such as a Reflective Radiant Barrier or Integral Condensation Control. There is not a good option for an underside of purlins vapor barrier, as it is nearly impossible to adequately seal it. Your only real solution, at this point, would be to use two inches of closed cell spray foam on underside of your roof steel.

 

DEAR POLE BARN GURU: My wife and I are building our post frame building ourselves. We’re building a loft living area on 1 end which I’m using 11.875 x 2.5 x 20′ long I-joist 16″ center.

My question is, My 6×8 posts are 8′ centers, can I attach a single 2x12x8′ between these posts and attach the I joist hangers to this to support the floor or will I need to double them like a header?

Thank you ALLAN in FORT ATKINSON

DEAR ALLAN: Any lofts, second or third floors being added to post frame buildings should only be done so under design of a Registered Professional Engineer – ideally whomever was Engineer of Record for your original sealed building plans. Rarely do concrete footings below building columns have adequate thickness or diameter to support additional loads being implied to columns. In most instances, beams for support of floor joists, I joists or prefabricated floor trusses will be limited in capacity by deflection, rather than ability to carry a given load. I can guarantee a single 2×12 is inadequate to support your I joists.

Your engineer will also determine proper number and size of fasteners to support beam to column attachments. At a minimum, with a 50 pound per square foot total floor load, columns every eight feet and a 20 foot span, each connection must support 4000 pounds of load.

Please, I implore you, do not attempt this floor design without proper engineering guidance – it could be lifesaving.

 

DEAR POLE BARN GURU: We are building a pole barn that is 20 by 32 with 8ft spacing. We are using steel trusses for this project, but our roof load for this county is 120lb per square ft., so how do I achieve this or how many trusses I would need to put in? Any help would help thank you. CHRIS in EMMETT

DEAR CHRIS: You should reach out to whomever provided your trusses to get an engineered repair. You should be able to have additional members welded onto what you have in order to meet required loads. On larger spans, this type of repair might not be possible.

 

 

This entry was posted in Lofts, Constructing a Pole Building, Pole Barn Planning, Trusses, Ventilation, Building Interior, Lumber, Columns, Pole Barn Questions, Pole Barn Design and tagged , , , , , , , on by .

Is Cor-a-vent a Right Product for Me?

Is Cor-a-vent a Right Product for Me?

Reader (and Hansen Pole Buildings’ D-I-Yer) LEE in IDAHO FALLS writes:

“Would this product https://www.cor-a-vent.com/purlin-vent.cfm be suitable for providing eave vents where no overhangs were designed. This product would be installed by recessing the eave strut (purlin) 1″ below the roof line and filling the gap with this product to provide air intake flow. Seems a better option than gable vents to get the best airflow.  It has a crush resistance of 7600# PSF.

Thanks”

 

For those who did not click on Lee’s link, here is some information from Cor-a-vent’s website:

“Is your insulation a wet blanket? Chances are it is. You know the problems all too well—cold side condensation on your metal roof and siding. You probably can’t see it, but it could be robbing you blind. Even slight amounts of moisture in blanket insulation can seriously reduce its R-value. Don’t count on vapor barriers—every seam and penetration has to be sealed perfectly, and how often does that happen on the job? Moisture vapor penetrates just about everything, and once it’s trapped, you have problems. The heating bill goes up, insulation can sag and the roof fasteners and purlins will start to rust. What do you do? Next building, you specify Purlin Vent™, from Cor-A-Vent—“The Leader In Innovative Rooftop Ventilation” ®

Purlin Vent is the first real system solution for venting behind roofing and siding in metal buildings. Made from sheets of crush proof profile extruded PP* Purlin Vent serves as an excellent thermal break between the metal roof and the purlin when foam insulation is used. For blanket insulation, Purlin Vent with Insulation Shield does two things. One, it keeps the blanket insulation away from the underside of the roof. Two, it creates a passageway for moisture to diffuse harmlessly to the outside.  When used with any of Cor-A-Vent’s metal roof ridge vent applications, it creates a very effective system for removing moisture and keeping your insulation dry.”

Mike the Pole Barn Guru’s take:

While your best possible attic ventilation system would be air intake at eave and exhaust at ridge, this product is probably not your solution.

Post frame buildings work due to shear strength of properly fastened skin – in your case steel roofing and siding. In roofs, greatest shear loads are at eave and ridge – this is why you see diaphragm screws on each side of every high rib in these locations. Cor-a-vent is designed for use in PEMB (Pre-engineered Metal Buildings aka ‘Red Iron’) where rigid steel frames are carrying wind loads from roof to ground. PEMBs do not rely upon a stressed skin for their structural integrity.

If this product was to be used on top of your eave strut, screw shanks would be able to work back and forth under wind loads, in Cor-a-vents thickness. Over time you could expect to develop leaks at your eave line due to screw slotting and, under critical loads, it could be possible for this connection to become overloaded.

Gable vents are realistically your option given your building has no eave overhangs to place vented soffit in.

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

Gable Fan, Clay Soils, and Condensation Issues

This week the Pole Barn Guru answers reader questions about use of a gable fan to prevent condensation, building with posts in clay soils, and addressing condensation issues in a three-stall garage.

DEAR POLE BARN GURU: I have been reading some post on your site about gable vents. I have a 40×80 building with spray foam on the bottom of the roof, which is sheeted with plywood. The walls have rigid foam and fiberglass. Question is, would an electric gable fan help or hurt condensation in the building, and is it even necessary. Much of the building will become heated and cooled living space. STEVE in SOMERSET

DEAR STEVE: It is very possible a humidity controlled electric fan would assist in reducing condensation, however before moving forward with it, I would recommend you consult with your HVAC provider, as a properly designed heating and cooling system can be set up to provide adequate air exchanges and control humidity.

 

DEAR POLE BARN GURU: I have heavy clay soil that does not drain. If I put posts in ground the bottom 2 feet will be soaked most of the year. Should I use concrete piers or will proper treated post be ok? MATT in MORRISTOWN

DEAR MATT: Having personally built a post frame combination garage/shop/mother-in-law apartment at our son Jake’s then home near Maryville, I feel your pain when it comes to Tennessee clay soil. Properly pressure preservative treated columns are not negatively affected by ground water, however you have other factors to consider before moving ahead with your build. You’ll want to read these articles discussing them: https://www.hansenpolebuildings.com/2019/06/post-frame-construction-on-clay-soils/ and https://www.hansenpolebuildings.com/2020/07/barndominium-on-expansive-soils/.

 

DEAR POLE BARN GURU: Hello, We are building a 3 garage pole barn and would like to know if you suggest the following:
A. Can you spray foam insulation to house wrap and do you leave the paper under mullions if removing the paper?
B. We have sweating on our house wrap and in our bay that will be mostly finished we put insulation boards which had paper on both sides and now will have to remove that side siding to remove it.
C. Our bay 3 floor is just stone, the others are concrete. We didn’t put a vapor barrier plastic under stone, so until spring when we remove stone and do this we were thinking of laying a tarp tight on stone to hold back any moisture into the rooms for humidity and condensation. What do you suggest? LAURIE in NEW YOUR

DEAR LAURIE: While there are some installers who will spray foam to a WRB (Weather Resistant Barrier aka house wrap), we do not recommend it https://www.hansenpolebuildings.com/2020/04/spray-foam-insulation-3/

vented-closure-stripIf you are getting condensation inside of your WRB it is due to excess moisture in your building. You need to eliminate or minimize sources of water vapor (seal any concrete slabs-on-grade if a well-sealed vapor barrier was not installed beneath). Proper ventilation from eave to ridge will also help to alleviate this challenge.

Provided you can well-seal a tarp, it is certainly a better option than just leaving raw stone exposed.

 

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

Venting an Attic

Saving Money When Venting An Attic?

While some of you may think I have been doing post frame buildings since dinosaurs roamed our planet, I can assure you this is not true. Now my youngest son, when he was pre-school aged, did ask me (in all seriousness) what was it like watching space aliens build Egypt’s pyramids!

When reader DOMINIC in FESTUS wrote his question to me, it got me thinking about when I first had a client ask for a building with insulation at ceiling level. While I truthfully do not remember, in my first 6000 or so post frame buildings (we are talking 1980s here) I doubt there were more than a handful.

Fast forwarding to today’s modern fully engineered post frame buildings and nearly every building – garage, shop, barndominium, etc., is going to be climate controlled to some extent and most of these have enclosed attic spaces with insulation to be placed at ceiling level.

Here is DOMINIC’s question:

“I will be building a 30×40 pole barn soon. I plan on putting a ceiling in with insulation. My question is on attic venting. It seems best practice is to use a ridge vent with vented soffits but are gable vents alone sufficient? It would be cheaper for me to just do gable vents.”

Your best practice is to have even airflow from eave intakes to ridge exhausts. If your building will have sidewall overhangs, you might as well take advantage of this. You COULD (as an alternative) utilize gable vents. Provided at least half of your gable venting is located in the upper half of the attic, you can get by with as little as 576 square inches of NFVA (Net Free Ventilation Area). To achieve this would require (3) three 20″ x 30″ gable vents in each endwall. This could prove unsightly, difficult to install and is unlikely to result in being less of an investment than ridge vents. NOTE: a 20″ x 30″ gable vent provides roughly 106 square inches of NFVA (not 20″ x 30″ for 600″).

Of course, me being me, I had to snoop our records to see if he had requested a quote from us – and indeed he had…..

In looking over your quote from us, you may also want to consider increasing your overhead door width from 14′ to 16 (or even 18′) as you cannot safely get two vehicles side-by-side through a 14 foot wide door. For sake of resale value, with a 14 foot door it will appraise as a single car garage, wider doors will nearly double your appraised value as it is a two-car garage then.

This entry was posted in Post Frame Home, Barndominium, Insulation, Pole Barn Questions, About The Pole Barn Guru, Building Overhangs, Ventilation and tagged , , , , , , on by .

Installing Steel Liner Panels in an Existing Pole Barn

Installing Steel Liner Panels in an Existing Pole Barn

Reader JASON in WHITEHOUSE STATION writes:

“ Hello! I have a post frame 30X40 Pole Barn that was built prior to me owning the house. Currently, the shop is not insulated. I would really like to insulate it, as it’s quite unbearable in the summer and winter. The building has soffit vents, a ridge vent, and two gable vents. With the way the building is set up with all that ventilation (possibly too much?), is putting in a ceiling with insulation on top my best bet? I know there are many options when it comes to insulation, but I am trying to determine what is best for my application. I am leaning towards 6 mil poly on the bottom side of the truss, ceiling liner panel over that with blown in insulation on top. My truss is 8′ on center. Is there a recommended length of panel I should use? Thank you for your help with this. I’m sorry if I asked too many questions.”

Mike the Pole Barn Guru responds:

Provided your building has roof trusses designed to adequately support a ceiling load, your best bet will be to blow in insulation above a flat level ceiling. If you do not have original truss drawings available to determine if they have a bottom chord dead load (BCDL) of three or more, then you will need to find the manufacturer’s stamp placed on truss bottom chords and contact them with your site address. With this information they should be able to pull up records and give you a yes or no. If you are yet unable to make this determination, a Registered Professional Engineer should be retained to evaluate your trusses and advise as to if they are appropriate to carry a ceiling and if not, what upgrades will be required.

If your building does not have some sort of thermal break between roof framing and roof steel (a radiant reflective barrier, sheathing, etc.) you should have two inches of closed cell spray foam applied to the underside of roof steel, or else you will have condensation issues (even with the ventilation). With trusses every eight feet (again provided trusses can carry ceiling weight), I would add ceiling joists between truss bottom chords every four feet and run 30 foot long (verify from actual field measurements) steel panels from wall to wall.

You do not have too much ventilation – and be careful not to block off airflow at eaves. You can omit poly between liner panels and ceiling framing.

This entry was posted in Pole Barn Questions, Pole Building How To Guides, Pole Barn Planning, Ventilation, Building Interior, Professional Engineer and tagged , , , , , , on by .

Insulating an Existing Post Frame Building Attic

We are in an era where climate control of brand new post frame buildings is extremely common. It is also much easier to insulate (or plan for it) at time of construction, rather than having to go back and do it afterwards. 

For new post frame buildings, here is my Ultimate Guide to Post Frame Building Insulation: https://www.hansenpolebuildings.com/2019/11/post-frame-building-insulation/.

Loyal reader DAMON in SPOKANE is fortunate to have some parts of his existing post frame shop made easy for retrofit insulation. He writes:

“Hi,

First I want to say I love your web site, the information I’ve been reading is invaluable! I am located in Spokane County. I have a 24x24x10 post frame garage that was here when I purchased the house. The walls have commercial girts R19 insulation. I would like to heat this garage and use it as a woodworking shop. Right now the ceiling is open and there is no insulation. The roof is sheeted with OSB, then felt then steel roofing panels. There is no ventilation or overhangs to install soffit vents. The roof has 4:12 pitch.

I am considering one of two options. The first is to spray foam under the roof decking with closed cell foam, about 2″ which would give me about an R14. This would mean I would have to heat a larger air volume all the way up to the roof. Is this an effective method? Will the closed cell foam seal everything and hold the warm air in efficiently? I supposed I could install a couple of slow turning ceiling fans to push the warm air back down.

The second alternative is to add a ceiling. I was able to confirm that the garage was built with bottom load trusses. I could install joists and an osb ceiling and then go with a blown in insulation, maybe R38. Because there is no ventilation I was thinking of adding large appropriately sized gable vents to provide the ventilation since I do not have soffit vents nor a ridge vent.

Of the two options, is one a better consideration than the other? I know you’re probably pretty busy, I appreciate any time you have to help me with my decision.”

Mike the Pole Barn Guru responds:
Thank you very much for your kind words, hopefully you have been entertained as well as informed!

As your building was built with trusses designed to support a ceiling, I would recommend you pursue this route. You would need to add gable end vents in the upper half of each gable with a net free ventilation area of at least 139 square inches per end. Please keep in mind this is not vent dimension, but net free area only.

Your building’s roof trusses probably do not have raised “energy heels” so it would be most practical to use closed cell spray foam insulation along two feet closest to each eave sidewall (applied to top side of ceiling finish). I would recommend you blow a minimum of R-49 across the balance of the attic area as this will meet minimum recommended attic insulation levels from www.energystar.gov. Your spray foam applicator can make recommendations for the thickness of his or her product.

Also, please consider using 5/8″ Type X sheetrock for your ceiling. It will be less expensive than OSB and provides some degree of fire resistance.

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

Venting an Attic Without Soffit Air Intake

Venting an Attic Without Soffit Air Intake

Loyal reader KEN has an attic space with only air exhaust points – a vented ridge, and no air intake. His dilemma, how to adequately ventilate his attic without vented soffits.

Ken writes:

“I finally was able to make contact with the manufacturer of the open foam like material used under my ridge as a vent. The following is cut and pasted from their technical material: Net Free Area 1”nom.Thickness 8.5 sq.in.per lin.Ft.per side (17 sq.in .per lin.Ft.ridge).  Since I have a 60 foot ridge, that would equal 1020 sq. in. or 7 sq. ft. 

Given the ridge vent, do you still recommend 3 sq. ft.  venting on each end?

You note that an 18×24 would provide 140 sq in (or 0.97 sq. in.), but 18×24 is 432 sq in.  Do the louvers and other components reduce that by a factor of 3, just wanting to confirm.  With a 3 sq. ft. requirement, I would need a vent nearly 3 times an 18×24.  Maybe it just comes down to not the ideal but what can be practically installed. 

In order to prevent rust at the cut line, should I caulk the outside seam where the louver comes through the wall?”

Mike the Pole Barn Guru writes:

Another way of thinking about ventilation – view it like a straw. Obviously with best (and most) straws each end has an opening. What happens when a hole exists somewhere between ends? A reduction occurs in your ability to draw up water or soda. A similar effect happens when different vent types are employed over a shared air space.

Air and water are similar, their flow follows a path of least resistance. In a properly designed and installed attic ventilation system air flow travels from intake vents to exhaust vents, flushing out warm, humid air along roof deck (think underside of roof steel). However, if two or more different types of exhaust vents (gable and ridge) are used above a shared attic air space, one exhaust vent will likely to interrupt air flow to the other. In this arrangement it becomes another intake vent for a primary exhaust vent – leaving large sections of attic space incorrectly vented.

I would be inclined to seal ridge vent off and utilize gable vents. Dimensions of gable vents are overall unit dimension, not net free area (reduced from overall size by both exterior framework and louvers). Each endwall may require multiple vents in order to achieve an adequate airflow.

Caulking cut edges of endwall steel would certainly not hurt. A suggested caulking would be TITEBOND Metal Roof Translucent Sealant.

 

 

 

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

Dear Guru: Can I Add to My Pole Barn in the Future?

DEAR POLE BARN GURU: I’m very interested in doing business with you, I just have a few questions. I originally asked for a quote of a pole barn of 200×50 I believe it was, my question is, can your buildings be added on to? Would we be able to start with something much smaller and then add on to the barn as we go? NOW IN NEW JERSEY

DEAR NOW: Yes, our buildings can be added on to. I would recommend the initial design be done with the idea of what the ultimate finished goal will be for size. Oftentimes, original structures are not structurally set up for the eventual expansion, which keeps the initial price low, but results in headaches and costs later, which could have been avoided with proper planning. A gabled roof will be the easiest roof style to work with when it comes to future expansion.

We have several customers who have done just as you suggest, adding on to one or both ends as they expand. Get the width you ultimately want, then adding length is much easier You can remove endwall siding, add on additional bays, and put the endwall siding back on. You may have to purchase more trims, but if steel siding, is easily reused for the addition.

And I always recommend – build as much building as you have space for and can afford economically, as whatever size you pick, it will never be large enough.

DEAR POLE BARN GURU: I’ve read ALL of your blogs!  Back to 2010. And love them. I write similar stuff in my business.

The question is do you have, or can you get, closures similar to ridge vent, but as a bottom closure to be used at the eave of a building without overhangs? BREEZY

DEAR BREEZY: Thank you for your dedicated readership and …good question! There is not such a beast, and even if there was, the net ventilation would be tiny – not enough to yield any positive results, as the only area which could have a vent would be just at the high ribs. The correct way to vent would really be with enclosed vented overhangs.

DEAR POLE BARN GURU:I have an existing pole building with badly deteriorating insulation and vapor barrier for the roof.

I plan to pull all of the old insulation and vapor barrier out to replace it.  I’d like to use the reflective radiant barrier / vapor barrier you recommend for new construction.  I’m considering pulling the metal roofing off to do it right so I don’t have to do it again later.

Do you recommend installing the reflective radiant barrier / vapor barrier between the metal roofing and purlins or between the purlins and roof trusses? DETERIORATING IN DELAWARE

DEAR DETERIORATING:
Place the reflective radiant barrier over the purlins and directly under the roof steel. You will need to use larger diameter, longer screws to reattach the roof steel.

DEAR POLE BARN GURU:Where can I buy Owens Corning Foamular Fanfold foam 1/4″ thick? A lot of my fellow RC plane hobbyists are having a hard time finding this stuff. Thanks in advance. FLYING IN FREMONT                          DEAR FLYING: Visit the Contractor Desk of any The Home Depot®. If it is not in stock, it can be ordered in within a matter of just a few days.

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