Tag Archives: A1V reflective radiant barrier

Condensation Control, Mother/Daughter Addition, and Vapor Barrier for Roof

Today the Pole Barn Guru answers readers questions about condensation control in a small garage with a gravel floor, the possibility of adding a “mother-daughter” unit to her house, and “ribbed vapor barrier” for a shed roof.

DEAR POLE BARN GURU: Recently purchased a metal garage kit, 24X26. No insulation. Two garaged doors. Gravel floor with plastic under grave. I am getting condensation on some days, that makes my cars, etc have like a dew on them.

My rib looks to be 1” and 7” between ribs. How do you install a wall vent with the ribs? JODY in ALTON

Machine ShopDEAR JODY: First step is to take care of your source. Pour a concrete slab on grade with a well sealed 10-15mil vapor barrier underneath. As you have no thermal break between your warm moist air inside building and roof steel, have two inches of closed cell spray foam insulation applied to underside of roofing. You would be better served to vent eaves and ridge, than just gable vents. If gable vents are your choice, look for vinyl vents with a snap ring as they can be installed on ribbed steel siding.

Using inward vent base edges as a guide, mark area to be cut on endwall steel INSIDE, make hole cut square with steel sheet (vertical cut lines parallel to steel ribs). Cut hole with appropriate tools.
Push vent base through hole in steel from inside.
Note word “TOP” on base when positioning. Vents installed with top side in any direction other than up will allow water to leak into building.
While holding vent base in place, snap face into base from steel exterior by pressing firmly (this takes two people).


DEAR POLE BARN GURU: I’m interested in building an attached mother/daughter addition to my home. Do you have plans for that? Approximately 600-700sq ft. NANCY in MONROE TOWNSHIP

Floor PlanDEAR NANCY: Thank you for your interest in a new Hansen Pole Building. Every building we provide is custom designed to best meet the wants, needs and budget of our clients. We offer a floor plan design service for folks just like you: http://www.hansenpolebuildings.com/post-frame-floor-plans/?fbclid=IwAR2ta5IFSxrltv5eAyBVmg-JUsoPfy9hbWtP86svOTPfG1q5pGmfhA7yd5Q 


DEAR POLE BARN GURU: We are having a 50×30 all metal building. We were advised to get ribbed vapor barrier for roof. We have searched everywhere. Is it called something else? SHANNON in OLEAN

DEAR SHANNON: We are also not familiar with any product known as a “ribbed vapor barrier”. We would normally recommend use of roof steel with an ICC factory attached (https://www.hansenpolebuildings.com/2020/09/integral-condensation-control-2/). If this is not an option (or if you are using closed cell spray foam directly to underside of roof steel), next choice would be a radiant reflective barrier – look for six foot wide rolls with an adhesive pull strip attached for ease of installation.


Seal Walls, Fill for Compaction, and Condensation Control

Let’s close out the week with another installment of Ask the Pole Barn Guru! First up is a resolution to seal up a building, followed by assistance with compacted fill, and finally an alternative to spray foam to control condensation.

DEAR POLE BARN GURU: I purchased a pole building from you last year and there was an error that I wanted an insulated building. So I will be insulating this myself. What keeps all the drafts and bugs out at the roof eve and lower edge of side panels? I am doing house wrap on the exterior walls. MARK in MOUNT VERNON

DEAR MARK: Communication – we as humans do so much of it and all too often do not fully convey our intentions. I am just as guilty as any other person, so do not feel like you are alone in this. This is one reason we strive to do everything in writing, so both parties are clear on each other’s expectations.


Also, successful construction is not measured by how perfect things went initially, but rather by how challenges are solved to arrive at a great end result.

Your roof eaves should be sealed with inside closures, provided with your building package, to install between fascia board and roof steel, so should not be an issue there. If you have not yet installed siding, same inside closures can be placed at bottom of walls, on top of your Weather Resistant Barrier to keep any little critters from entering steel high ribs in your 1/4 inch space between base trim flat and bottom edge of wall panels.


DEAR POLE BARN GURU: I’ve worked with a Hansen Building Designer, ordered my building, and materials will start arriving in two weeks. Looking forward to it, but also a little bit ‘trepidated,’ as it’s my first post-frame build (I completely remuddled a 100 year old farm house at our last place, so that’s what I have for previous experience).

My question has to do with the compacted fill that goes onto my cleared site after the poles are concreted in. Is crusher run gravel appropriate, or is a different type of gravel recommended for better drainage (I’m not familiar with the options, so please be specific if so)?

Also, please see the attached photo of the cleared site along with a drawing I created based on what I *think* are the correct dimensions based on reading the Construction Manual and a number of your blog posts. Note that I’m planning on a 5″ thick concrete floor, and have indicated same in the drawing at exactly 5″. ED in SUMMERTOWN

DEAR ED: Awesome drawing! You should have no difficulties in assembling your own beautiful building, as I can tell you are already reading directions!

Crusher run should be adequate for your sub-base. Most important is to get any clay removed from within upper levels of your grade and to have good compaction. Top two to six inches of your fill should be clean and drained sand or sandy gravel, again well compacted.

Photos: https://hansenpolebuildings.com/uploads/polebarnquestions/7bea6f6c3d75e192515b8bd12303c72c.jpg


DEAR POLE BARN GURU: If not spray foam on the underside of metal roof then I saw you recommend reflective siding insulation. Would that suffice in lieu of spray foam?


DEAR DYLAN: My first alternate choice would be to use an I.C.C. (Integral Condensation Control) https://www.hansenpolebuildings.com/2020/09/integral-condensation-control-2/ easy to install and no seams to worry about. Next choice would be a Reflective Radiant Barrier – we have it in six foot wide rolls with an adhesive pull strip to seal joints. Contact Materials@HansenPoleBuildings.com for delivered pricing (rolls are 128′ long).




How to Install Roof Reflective Radiant Barriers

How To Install Roof Reflective Radiant Barriers


“Can you please tell me how the reflective radiant barrier is applied? Does it go directly on top of the fully recessed purlins and then the steel is screwed over top of that? Is it applied vertically or horizontally? All of the videos that I’ve seen say there needs to be an air space between. It should have been stressed to me at the time of purchase that this was a critical material of the construction of my shop and it was not portrayed to me in that manner. I purchased it separate and I am at that step.  I believe the sales person must have been new because a lot of mistakes were made.”

Any steel roofed building should have some sort of provision made to prevent warm moist air from inside contacting cooler roof steel and condensing. There are many possible solutions to this – two inches of closed cell spray foam, an integral condensation control or a reflective radiant barrier being most popular (as well as being aligned from greatest to least in terms of financial investment of materials). Chapter 14 of your Hansen Pole Buildings’ Construction Manual does give detailed instructions for this installation.

Post frame buildings have a myriad of possible options and accessories, as well as being utilized for a plethora of end uses. Considerable discussion is most often involved prior to an order being placed – and on occasion there are cases where important features are lost during discourse.

We do attempt to avoid situations such as yours and you may recall having approved this Dripstop to help control roof condensation.
Here are your requested installation instructions:

Start roof reflective radiant barrier at same building end roof steel installation will begin. galReflective radiant barrier roll end begins flush with eave strut outside edge. Reflective radiant barrier leading “long” edge begins flush with building end truss outside. 

Reflective radiant barrier is installed to run eave to eave over ridge. Splices are best made directly on fully recessed purlin tops.  

Other than to make a roll end square, starting edge will remain untrimmed.  Start flush at eave strut outside edge.  Opposite end is cut flush with opposite eave strut outside edge (or ridge purlin upper edge for translucent or Vented Ridge applications).

Using a minimum 5/16” galvanized staple, staple through reflective radiant barrier to eave strut top.  As an alternative to staples, 1” galvanized roofing nails (with big plastic washers) also work well.  Roll out reflective radiant barrier across fully recessed purlins (up and over ridge) with aluminum side up and white side down (towards building inside). 

Pull reflective radiant barrier past opposite eave strut edge and staple to top. Trim roll off flush with opposite eave strut outside edge.  

Install next roll in same manner, stretching roll tightly, align properly and close butt sides.

For A1V reflective radiant barrier with an “adhesive tab”: These rolls have an approximate 1” tab (without air cells) extending along one reflective radiant barrier roll long side.  At a seam, where two reflective radiant barrier rolls are joined, pull tab across adjacent roll by 1”, remove “pull strip” from adhesive, and firmly press two rolls together. Properly installed, each roll will have a 72” net coverage.

For square edge rolls, use a butt joint and seal seams properly with tape.  

2” white vinyl tape or a silicone bead can be used to make permanent seams between ends and reflective radiant barrier roll sides. 

For maximum air and vapor tightness, keep perforations in reflective radiant barrier to a minimum. Seal all perforations with reflective radiant barrier tape. 

Exaggerated claims are often made for insulating value of reflective radiant barriers and all of them rely upon a dead air space in a completely sealed scenario – great in a laboratory situation, however impossible to achieve in real life building construction. Reflective radiant barriers should be looked upon (when seams are properly sealed) as a condensation deterrent.