Tag Archives: thermal break

When the Problem is Not the Problem

When The Problem, Is Not The Problem

Captain Jack Sparrow’s quote is close in this instance. Please read on…..

RYAN in MISSOURI writes:

Hi Mike – I spoke with Brenda at your office and she said you may be willing to help me out. I don’t expect you to just give me free advice though, so if you were willing to provide me with some feedback on my “project”, I would like to pay you via Venmo or maybe your office could work up an invoice and I can pay you guys with a credit card. 

I built a 36×48 pole barn 5 years ago and didn’t account for adequate ventilation and now I want to fix the problem (I’m sure you’ve heard that line countless times before). I read one of your blog posts to get a head start on working up a plan of attack to keep it dry in there. I’m hoping you could check my work and either take a phone call from me or provide guidance via email (again, I can shoot you some money for this, please just let me know what sounds acceptable to you). 

Specs on the barn (I’ve included some older pics from before I installed the gutters and the electric below):

  • Location: central Missouri
  • Dimensions: 36′ wide (gable and door end) x 48′ long
  • No overhangs or soffit 
  • Two 8 ft ridge vents
  • Gutters down the eave/length sides to push water away from the “foundation” 
  • Currently no vents on the eave/length or gable sides or anywhere really… just some gaps around the trim and the base of the building where you can see daylight. 
  • The barn has electricity and the floor is just gravel. I have a junction box run to the gable on the south side (over the door ready to accommodate a vent fan). No animals inside. Just old tractors, some tools, and four wheelers. I don’t plan on putting in concrete or any HVAC. Things out there can get hot or cold, I just don’t want it raining from the ceiling anymore. 

Using your blog post, I tried to calculate what I would need as far as the CFM rating of the fan and the square inches of vent space (table of numbers below)

Questions: 

  • Before installing a fan, I should ask: is a fan even necessary? Seeing as I don’t care about HVAC, temperature or even critters getting in there, could I get by with just strategically placed vents and wind? 
  • If I do need a fan to generate enough circulation, does my math below look ok? 
  • Would the Airlift T16 with a 3060 CFM adjustable fan speed and a humidity detector or something like it work ok? 
  • Where would you recommend I place the vents (and I’m happy to go overkill on them if needed) in order to achieve the best results? 

Thank you so much for your time!”

Mike the Pole Barn Guru writes:
Thank you for your generous offer of payment Ryan, however I answer all sorts of similar questions for free.

Now, the good news and bad news….

Good news is you do not have a ventilation problem, no reason to invest in any possibly expensive power ventilator fans.

Bad news – as you have found out, it rains from your ceiling. What you have is a condensation problem. Warm, moist air inside of your building is rising. It contacts with cooler roof steel, condenses and rains. This is much easier solved at time of construction than now (as well as less expensive). Roof steel ordered with an Integral Condensation Control factory applied would have been highly affordable, as well as easy to install.

Short of removing and reinstalling your roof steel to add a thermal break between purlins and steel (both costly and labor intensive), I would recommend having two inches of closed cell spray foam professionally applied to the underside of your roof steel.

When you do pour a concrete slab inside, be sure to add a well-sealed 6mil or thicker vapor barrier underneath.

Insulating a Partially Climate Controlled Building

Insulating a Partially Climate Controlled Post Frame Self-Storage Building

Reader KEVIN in HUMBOLDT writes:

“ I’m designing a post frame building for self-storage that will have non climate control units around the perimeter of my building with climate controlled units in the center, accessed via a hallway down the center of the building. The entire building will have a metal ceiling. The walls between the climate controlled area and the non-climatized units will be insulated with fiberglass with a vapor barrier between insulation and wall metal on climatized side. I’ll have fiberglass in the attic space above climatized area with vapor barrier between insulation and ceiling metal. If my math is correct on a 58×174 building, I need 4845 square inches in NFVA (net free ventilation area) exhaust and intake. My soffit and ridge vent combo will provide 6960 NFVA exhaust and intake. I have 2 questions. First, do I still need a thermal break under my roof steel? Second, I’ll have 2×6 purlins on edge, recessed btw trusses so, would it be advantageous to install a radiant barrier or house wrap to the bottom side of my purlins, simply for smooth airflow from my soffit vent to ridge vent? Just wondering if purlins blocking air path up the roof is anything to be concerned with. Thank you.”

Mike the Pole Barn Guru replies:

You need some provision for condensation control below roof steel – easiest would be to order roof steel with an Integral Condensation Control factory applied. In Tennessee you should not have a vapor barrier between steel ceiling liner panels and blown in fiberglass attic insulation. Placing a barrier on the underside of roof purlins does not appear to make a noticeable difference in performance of attic ventilation. Although you did not ask, you should have a well-sealed vapor barrier (6mil or greater) and R-10 EPS insulation under slabs (even in non-conditioned areas) to minimize potential for condensation on top of slab.

Vapor Barrier for a Ceiling

Reader GEORGE in LOUISVILLE writes:

“I am looking to install tin on the ceiling of my 54 X 75 pole shed. I was wondering if 6 mil plastic sheeting with all seams taped would work for a vapor barrier? My concern is not to have it rain in my building after the tin is up and the heat is on.”

Mike the Pole Barn Guru:

Well George, this answer is not going to be nearly as simple as your question.

Prevention of internal rain (condensation) is going to be a function of several aspects.

#1 Controlling source – if there is not a well-sealed vapor barrier under your concrete slab on grade, you should be planning on two coats of a good sealant for it. If you do not know if there is a vapor barrier under it or not, leave a wrench on it overnight. Next day, pick the wrench up and if there is a dark place on the floor surface where the wrench was, you have no under slab vapor barrier.

#2 Source of heat – some heat sources add significant amounts of water vapor into your internal air (propane being a prime offender). Know what you are getting into before it becomes a challenge you do not want.

#3 How are you currently controlling condensation? If your building has a thermal break between purlins and steel roof – excellent. If not, your best solution is going to be two inches of closed cell spray foam applied to the underside of roof steel. This is not an inexpensive solution, but it is more practical than removing roofing, adding a thermal break, and reapplying roofing (plus roofing never goes back on as well as it was originally installed). Plan on $4000 to $4500 for closed cell spray foam.

vented-closure-strip#4 Ventilation – you are going to create a dead attic space above an insulated ceiling. If it is not adequately vented you are going to have problems. Best combination is vented eaves and ridge. Your building will require at least 1944 square inches of net free ventilation area (NFVA), distributed equally between eave and ridge. If this is not possible (building has no sidewall overhangs), then your choice is limited to gable vents and it will take many of them to provide adequate NFVA.

#5 You are in Climate Zone 5. This means a Class I or II vapor retarder is required for the interior side of framed walls. This could be 6 mil polyethylene (Visqueen) or Kraft-faced fiberglass batt insulation. For your ceiling a plastic vapor barrier should only be installed in vented attics in climates with more than 8,000 heating degree days. In Nebraska, heating degree days for a normal year is 6322.

Integral Condensation Control

With steel roofing for barndominiums, shouses and post frame (pole) buildings comes condensation.

When atmospheric conditions (in this case temperature and humidity) reach dew point, air’s vapor is able to condense to objects colder than surrounding air temperature. Once vapor condensing occurs, droplets are formed on cool surfaces. This is partly why warming a vehicle’s windshield with a defroster can prevent glass ‘fogging’.

When a building’s interior air meets these conditions, air vapor will condense to cool surfaces. Steel roofing cooled by exterior air temperature often provides this surface. Droplets formed will combine as they contact one another, continuing to do so until they are too large to be supported by surface tension. At this point, dripping will occur, essentially raining on your structure’s contents. 

Commonly (when addressed at all during construction) solutions to this problem have often involved creating a thermal break. A thermal break reduces contact between a structure’s warm interior air and cooler metal roofing, thereby reducing or eliminating overall condensation. Installing a reflective radiant barrier, often termed Vapor Barrier, involves laying rolls of faced ‘bubble wrap’ across your building’s purlins prior to roof steel installation. Ideal weather conditions are required for this as even a slight wind can make this a challenging or altogether impossible task. This can cause jobsite delays and may bring progress to a halt while a structure remains unprotected to weather. Even when ideal weather conditions are present, installing a reflective radiant barrier can be a very dangerous task, requiring builders to expose themselves to awkward material handling on a building’s bare roof framing. These risks and delays often generate additional costs for both owners and builders, but have often been necessary with reflective radiant barrier being the only relatively affordable option to prevent interior dripping. 

New materials and production methods offer a better solution. Utilizing polyester fabric’s absorption characteristics and their integral application during roll-forming, most better quality steel roofing roll formers offer a ready-to-install roofing panel with integral drip-protection. I.C.C. is a pre-applied solution reaching jobsites ready for immediate installation. Delays and increased jobsite workload caused by problems associated with radiant reflective barriers are eliminated by this product. Also, due to this solution’s simplicity, panels with I.C.C. install using the same methods, fasteners and time similar panel-only installations require. No changes to installation processes are necessary, with an exception of time and effort saved. 

It works because this polyester membrane simply retains liquid until atmospheric conditions allow it to be re-evaporated. This is because polyester is hydrophilic, meaning water is attracted to it. It acts as a wick, harmlessly absorbing condensing vapor. Rather than preventing condensation, it provides an absorbent layer to detain condensing vapor until it can re-evaporate as temperatures increase and humidity decreases.

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.

More Condensation Fun

Long time readers should be thoroughly drenched with solutions to condensation issues by now. As post frame construction has moved off farms and into suburbia, climate control has brought with it a plethora of condensation challenges.

Reader KRYSTA in SPOKANE writes:

“Hello! 

I have a pre-existing pole building that I am having a ton of trouble with. It is partitioned into two rooms, the back room is heated to around 50F. The attic space/loft space has a lot of condensation and I cannot seem to get this fixed. I have tried a lot of solutions, none of which have worked. I know that you build these types of buildings so I am hoping that you can recommend someone who might be able to come in and look at this issue and help me with a solution that works. I have no idea what to do next and I am a local business owner – my business is at a standstill right now until I can get this issue fixed. If you can recommend any general contractor, or anyone who might have expertise in pole buildings who I can contact I would greatly appreciate it. 

Thank you so much!”

Mike the Pole Barn Guru writes:

To control your condensation challenge you need to either remove warm moist air from inside your building, prevent this air from becoming in contact with surfaces at or below dew point, heat and/or ventilate. Here’s a brief summary, followed by solutions specific to your case: https://www.hansenpolebuildings.com/2019/02/how-to-reduce-condensation-in-post-frame-buildings/.

If you do not have some sort of thermal break below your pole building’s roof steel – two inches of closed cell spray foam should be applied. This process will be best done by a professional installer. Make certain to not block ventilation intake and exhaust points.

Unless you know for certain a vapor barrier was placed under your building’s concrete slab, seal the floor. https://www.hansenpolebuildings.com/2019/02/how-to-properly-apply-post-frame-concrete-sealant/ and https://www.hansenpolebuildings.com/2018/11/siloxa-tek-8505-concrete-sealant/.

Vent any dead attic spaces. https://www.hansenpolebuildings.com/2018/03/adequate-eave-ridge-ventilation/.

Heating your building to a temperature above dew point will also solve this issue. Avoid heating with propane, as it adds moisture to the air.

Making Framing Work With Bookshelf Girts

Making Framing Work With Bookshelf Girts for Insulation

A most simple method to achieve a deep insulation cavity in post frame building walls is to use bookshelf girts, but how to make framing work?

Some quick background reading on commercial girts: https://www.hansenpolebuildings.com/2011/09/commercial-girts-what-are-they/.

Reader BRANDON in ST. JOE got today’s discussion going when he wrote:

“Hi there. I’m going to be building a post frame house and got a quote form Hansen for my building. Question is with the bookshelf Girts if they are 2x8s which measures 7 1/4” on 6×6 post that is 5 1/2” plus your 1 1/2” grade board will you notice the 1/4” difference.”

In an ideal dream world every 6×6 column would measure exactly 5-1/2 inches square. However lumber comes from trees, and trees are organic and tend to have a certain degree of variability. Rarely are timbers going to be dried after being milled, other than by nature. As such, they most usually start off being cut slightly over-sized in order to allow for shrinkage hopefully ending up with a 5-1/2 inch dimension.

I have seen builders attempt to use 2×6 bookshelf girts with 6×6 columns, if posts are perfect dimension then both sides can be set flush and surfaces for siding and interior finish are smooth. It does involve some extra work insetting things like splash planks, eave girts, headers, etc., as well.

I tried this in my own garage I had built in 1991. My posts were not perfect dimension, they were big! I had to stop drywall up against each column and then texture over posts. Trust me, it was a PITA (Pain In The Axx).

An easy fix – oversize girts by one dimension, using a 2×8 with a 6×6 column as an example. Chances are excellent columns will measure 5-3/4 inches in depth or less. If less, drywall (or other interior finish such as OSB or plywood) can be run directly across thinner columns with no adverse challenges.

I would recommend using closed cell rigid insulation sheets inside of framing, behind drywall, to create a thermal break.

Dear Guru: What Type of Insulation?

DEAR POLE BARN GURU: Good morning, Mike … I have a question for you.

I’m trying to decide between a 30×40 barn and a 60×40 barn. It would have a gambrel roof with a loft. 16′ wide sliding door in the center of the short ends.

All other things being equal, what is the cost difference between 30×40 and 60×40?

Or is there a size that’s more economical?

Thanks, Mike T. in Kershaw, SC

DEAR MIKE T.: Having to design the loft to support hay weight is not so much of a challenge as it is expensive. For sake of discussion the comparison was done a full loft, however it may be more practical to only have the loft in the center.

There is an economy of scale with pole buildings. For practical purposes, the price per square foot is going to decrease as the building footprint increases (until clearspans become very wide). I’ve also never had a client tell me their new building is “just too big”!

In your particular case, you could double the size of the building, while increasing the investment by only about 2/3.

Mike the Pole Barn Guru

DEAR POLE BARN GURU: Renovating our pole building arena is an undertaking.  We were quoted $70k (which included windows to replace the plastic) so we are doing it ourselves. I expect materials to run about $25k in the end.  The company that sold me the metal ceiling panels based out of Kentucky told me that people in his area do it all the time and that the best way to go is with blown insulation, as fiberglass batting is a lot more time consuming to install.  I decided against spray foam because it is toxic to begin with and then they put fire retardants in the mix which is even more toxic.  Plus it is expensive.

What will happen if we don’t have a “thermal break” on the underside of the metal roof? There will be a lot of condensation falling on the blown insulation?  We have a roof vent which I guess is correctly installed because we never have water coming in even during the most violent and heavy of rain storms. Isn’t this vent enough to prevent condensation?

If a herd of animals lived in the building, then I would worry about condensation, but there will be maximum 2-4 live beings in there at one time.   Removing the roof to install a reflective radiant barrier is not an option.  How about covering the underside with “Tyvek” the stuff houses are wrapped in?  Are you saying the blown insulation on the ceiling will not do its job without this thermal break on the roof, or is it the condensation you are concerned about?   What does the reflective radiant barrier need to reflect?  Cold coming from outside, or heat coming from outside?

We have blown insulation in our 14 year old house.  I guess it is newspaper.  It works a charm.  We’re on a hill and it can blow out there and we’re cozy inside.  One can buy cellulose from Lowe’s or Home Depot and they lend you a machine to install it.   I was worried that wind from the roof vent would blow it around.  I was also worried critters would nest in it, although we have covered such access with 1/2″ wire mesh.  Nonetheless, critters are very resourceful about getting into things.  I was worried that if it got wet it would get moldy.  My daughter is very sensitive to mold.  Best thing is it stays dry….and like I said, we never had rain come through that vent, although when the conditions were right, we’d get a bit of snow blown in.  We have a lot of snow now, and no snow in the arena.  So it has to be special conditions. I thought of covering the blown insulation with tarps to protect it from wind or moisture.  Is that a good or bad idea?

BTW, we have no intention of heating the arena.  The goal is to have it warmer in there than outside….hopefully a little above freezing.

I guess for the walls we will use fiberglass.  The plastic panels will be replaced with double glazed “picture” windows (they don’t open) and will run the length of about 2/3 of the arena at 2′ high.

A trainer we met from Maine said he insulated his riding arena and it really helped keep out the cold.

I’m wondering what will happen in summer.  Will it keep out the heat, or trap it?

It’s great communicating with someone who knows what they are talking about.  I’d be happy to compensate you for your expertise.

P.S.  Here’s a fiberglass story.  The owner of a horse boarded at our farm had a plumbing leak in her basement.  The plumber came and fixed the leak and left.  Several weeks later she developed itching sores all over her body.  She woke up one morning with arms so swollen she could not bend them and a face twice the size of normal.  She went to the ER and they told her a dust allergy, so she threw out all drapes and mattresses, etc. and cleaned the carpet and whole place.  However, it didn’t help and she landed in the ER again.  Meanwhile they found out that the plumber had pulled away fiberglass insulation from the broken pipe, and because of the leak it was all wet.  He didn’t remove the wet fiberglass and so mold developed, and with the furnace down there blowing hot air (with the mold) all over the living space it made her VERY sick.  She moved out immediately and had to take a lot of nasty drugs, and she is still not well.  Plus, inhaled fiberglass is a known carcinogen, as you probably know.

A GREAT thing to insulate with is wool.  But who can afford it?  They do make wool “bats” for the purpose though.  CINDY

 DEAR CINDY: Without the thermal break under the roof steel, there will be condensation on the underside of the roof steel, which will result in rain upon the attic insulation. Ventilation alone may cure some, but not all of the condensation problems.

The major source of the warm moist air rising is the ground under your building (evapotranspiration). According to www.ScienceDirect.com the average value of the moisture evaporation with uncovered ground is 0.33 to 0.53 gallons per hour per square foot. For a fairly typical 60 by 120 foot riding arena, this could be between 57 and 90 thousand gallons per day!!

Housewraps like Tyvek are not vapor barriers – they are designed to allow moisture to pass through.

Reflective radiant barriers just happens to be a very cost effective thermal break. The aluminum facing on the exterior reflects radiant heat in the summer, keeping the building cooler.

Insulating your building will keep it cooler in the summer, there is no question there. As to the effectiveness for keeping things warmer inside, without a heat source the air inside will be at or near the temperature on the outside.

And thank you very kindly for your offer of compensation. I do my best to provide quality information for the good of the industry as a whole. If you feel I have been of service, please feel free to share the link to this blog with others.

Mike the Pole Barn Guru