Tag Archives: foam boards

A Garage Apartment, A Moisture Problem, and Insulating a Ceiling

Today’s Pole Barn Guru answers questions about building a garage apartment aka a “Shouse,” how to address a moisture problem, and the best way to add insulation to a ceiling.

DEAR POLE BARN GURU: Can I design a garage apartment pole barn? JAY in HINTSVILLE

DEAR JAY: You may not have this ability however we have experts who can assist you. To develop a workable custom floor plan, designed specifically to meet your wants, needs and budget please use this link: http://www.hansenpolebuildings.com/post-frame-floor-plans/?fbclid=IwAR2ta5IFSxrltv5eAyBVmg-JUsoPfy9hbWtP86svOTPfG1q5pGmfhA7yd5Q

 

DEAR POLE BARN GURU: Live in the Midwest, have a 54 x 36 pole barn well insulated, walls, and ceilings. When it rains a lot I have a moisture problem, My building is approx. 1950 Sq. Ft. I found a dehumidifier that covers 3,000 sq. ft. I was thinking about putting one in the pole barn, it can run continuous if I put a hole in the side, for a drain, and let it drain out, just leave it running on its own as it needs to. Is this Ok to do to solve my issue? RON

DEAR RON: A dehumidifier may resolve your building’s symptoms, however not its problem. As this is a function of rain, I am led to believe you need to eliminate or reduce your moisture source. If your building does not have a vapor barrier under your concrete floor, seal top of floor. If you do not have rain gutters install them and ensure runoff is directed well away from building. Make sure ground outside of building is sloped away at least 5% for 10 or more feet.

 

DEAR POLE BARN GURU: I have a 32X46X15 pole barn with purlins attached to the outside of the 6×6 beams. The barn has soffits and a vented ridge cap and is set up for a ceiling. I have since decided to keep the rafters exposed and have questions about sealing up the soffits and ridge cap but leaving several small openings in the ridge cap to allow for humidity to escape.

How much should I leave open on the ridge cap and should I totally seal off the soffits? Will it be ok to leave the beans and rafters exposed, putting a vapor barrier in between the beams and the rafters?

What are your thoughts on 2in foam with no vapor barrier glued directly to the metal in between the purlins every 2feet? Then another 2in foam board with a vapor barrier placed on top of that screwed to purlins and can spray foam the edges and gaps? Thanks for all your help! MARK in VALPARAISO

DEAR MARK: My response is with a thought you are trying to climate control your building to some extent. Your proposal to use two inch-thick foam insulation board sounds to be highly labor intensive as well as being fraught with challenges in trying to achieve a complete air seal. Any air gaps would allow for warm moist air from within your building to not only condense against your building’s steel cladding, but also to remain trapped there, potentially being a cause of premature degradation of steel panels.

I would recommend you look towards closed cell spray foam as a solution for both insulation as well as condensation control. You will want to completely seal both eave and ridge then have at least a two inch thick layer of closed cell foam sprayed on interior face of roofing and siding. A mechanical dehumidifier should be used to control relative humidity with your building.

 

 

 

 

Rigid Insulation Boards

Foam boards—rigid insulation boards—can be used to insulate almost any part of your pole barn, from the roof down to the foundation. They provide good thermal resistance. Foam board insulation sheathing reduces heat conduction through structural elements, such as wood wall girts and roof purlins.

There are some who would feel the best application of these products is to the outside of wall girts and purlins, directly beneath the wall and roof steel. Doing so can create a huge structural problem with pole buildings.

A properly designed pole building utilizes the steel skin to create a diaphragm. The steel skin functions like the shell of a uni-body car or modern jet aircraft.

When rigid insulation boards are applied to the exterior framing, the screws must be ordered appropriately longer to attach the siding or roofing. When the pole building is then subjected to racking loads from wind or seismic forces, the shank of the screw between the steel skin and the underlying wood – which passes through the rigid insulation boards, may bend or break, resulting in a compromise of the building’s structural integrity.

The most common types of materials used in making foam board include foam building insulationpolystyrene, polyisocyanurate (also known as polyiso) and polyurethane.

Molded expanded polystyrene (MEPS) is a closed-cell material which can be molded into many everyday items (think coffee cups and shipping materials), or into large sheets of foam board insulation. MEPS foam board insulation is commonly known as beadboard.

To make beadboard, loose, unexpanded polystyrene beads containing liquid pentane are mixed with a blowing agent and poured into an enclosed container. The mixture is heated to expand the beads many times their original size. The beads are then injected into a mold. Under more heat and pressure, they expand to become foam blocks, which are shaped as needed.

The physical properties of MEPS foam board vary with the type of bead used. It’s manufactured at various densities, depending on the application. Beadboard for roofing materials has to be dense enough to walk on without damage; wall insulation foam boards are several times less dense than roof boards. R-values range from 3.8 to 4.4 per inch of thickness.

MEPS foam board is available with a variety of facings. Since spaces between the foam beads can absorb water, a vapor diffusion retarder is needed if water transmission through the insulation might become a problem. MEPS foam board also is often used as the insulation for structural insulated panels (SIPS) and insulating concrete forms (ICFs).

One of my personal pole buildings, at my home, utilizes rigid insulation boards, ICFs, on 2-1/2 walls of the lowest level.

Extruded expanded polystyrene (XEPS) is a closed-cell foam insulation similar to MEPS. To make it, the polystyrene pellets are mixed with various chemicals to liquefy them. A blowing agent is then injected into the mixture, forming gas bubbles. The foaming, thick liquid is then forced through a shaping die. When cooled, the panel is cut as required.

XEPS is more expensive than MEPS. Like MEPS, the R-value depends upon the density of the material and is generally about R-5 per inch. It’s also much more consistent in density and has a higher compressive strength than MEPS, making it better suited for use on roofs or for wall panels. Extruded polystyrene also has excellent resistance to moisture absorption.

Like MEPS, XEPS is available with a variety of facings and is also often used as the insulation for SIPs and ICFs.

Polyiso and polyurethane are very similar, closed-cell foam insulation materials. Because both materials offer high R-values {R 5.6 to R 8} per inch of thickness, a thinner foam board can be used to achieve the required thermal resistance. This can be an advantage in limited space applications.

Polyiso foam board insulation is available in a variety of compressive strengths. Compressive strength refers to the ability of a rigid foam board to resist deformation and maintain its shape when subjected to a force or load. Also, polyiso remains stable over a wide temperature range, making it good as roofing insulation. When used with a laminated aluminum foil facing, polyiso foam board provides an effective moisture or vapor barrier. These foam boards can also be used to make SIPs.

The maximum performance of rigid insulation boards depends heavily on proper installation. If you want to install it yourself, obtain and carefully follow instructions and safety precautions from the manufacturer. Also check local building and fire codes to see if it’s allowable to use foam board insulation in your new pole building. If so, are there any special requirements for using it?

Hold these thoughts until tomorrow – and I will delve into how to use foam board in foundations, using a fire barrier and a whole lot more more.  Stay tuned!