Why Put Fanfold Polystyrene Under Siding

And even though some manufacturers call it rigid foam insulation for the purpose of vinyl siding it basically has the same insulating value as a piece of plywood.

Why put fanfold polystyrene under siding.

I have not seen any studies that show how well tape adheres to foam over the long haul. Dupont has said on their website and product flyers that if using both fanfold and housewrap and committed to both put the tyvek housewrap over the fanfold but they actually recommend assuming the insulation is totally closed cell with very low absorption rate putting the insulation directly under the siding overlying dupont drainwrap which is designed to provide a better drainage path between the two than regular housewrap. As many things in building science go you my dear reader have to learn something. Let s take a look at each.

The house was build in the 19970 s 2 4 walls and pink insulation between the studs. I get asked if this or that in the in the cavity works as well as foam under the siding. Eps is used under roofing over foundation walls and beneath siding. In reality rigid foam board which sometimes comes in fanfold usually only has an insulating factor of r 1 and does not add any appreciable insulation effect to your home.

However another important consideration is what to put under your siding. It provides an r value of 4 per inch of thickness and is the cheapest type of foam board insulation. Will this cause any condensation issues. This is the same stuff your disposable coffee cup and is made out of and it s used to protect fragile items in their packaging.

This creates a horizontal seam every 4 feet. Installing foam insulation under vinyl siding is a wise choice for homeowners who are seeking to protect their homes against moisture infiltration as well as improve energy efficiency. Fanfold foam residing board is a thin perforated extruded polystyrene foam board faced on one side with a plastic film facer and combines proven xps foam technology with a unique design to enhance the application of new or replacement siding. I thought i should show why continuous foam under the exterior siding is so important.

The house has wrap under the siding. It also serves as an air barrier. The windows are being removed and moved out the 2 to line up with the foam board. This generally means choosing between tyvek homewrap made by dupont since it is the most popular brand and exterior fanfold insulation.

This foam board insulation is the rigid pink or blue panels that can be found at home centers in many different thicknesses. Fanfold foam residing board. By glenn hooper june 2 2015.