Crawlspace Insulation – Expanded Polystyrene (EPS) Foam Insulation

To achieve superior thermal performance, durability and protection from the elements our crawl space floor is a multi-layered assembly. First, the space was filled with 4 inches of gravel for drainage, followed by heavy duty polyethylene sheeting as a vapor barrier. The third layer is 3″ thick expanded polystyrene (EPS) foam sheeting for insulation.

Custom cutting EPS to fit our crawl space floor is relatively easy.

A tight fit is the goal.

We are using a high density EPS (2#) for strength so that we can pour a 2.5″ to 3″ slab of concrete over the top to protect the EPS and provide a highly durable, drainable and cleanable surface for finished crawlspace floor.

The completed crawlspace floor assembly will have a modelled insulation value of over R14. This definitely helps meet the Passive House thermal envelope requirements. We are on our way to passing the “heat it with a hair dryer” test!

Because EPS (expanded polystyrene) is mostly air, it makes an excellent insulator. The thousands of air pockets create a very effective thermal barrier. EPS is very stable and maintains almost 100% of its original R-Value over time which helps in fulfilling our goal of building for durability. 100% of the EPS can be recycled. Since the Insulated Concrete Forms are also made from EPS that means the whole crawlspace can be recycled …in a few hundred years. 🙂 Now on to Step 4.