Category Archives: PH Insulation

Air Tight Envelope: Options for sealing

We’re shooting for the Passive House Standard on this project, which means one of the big targets is that it’s got to be really air-tight. Below 0.6 ach50, to be precise. Since this is the first time we’re attempting this, we’re testing a few different strategies. One of the materials we’re using is closed-cell spray foam. Here we’re spraying it between the floor beams and the crawl space to completely fill the gap between the rim joist and our nicely insulated stem walls. The idea is that the spray foam insulation will create both an effective continuous thermal barrier and will also seal any gaps we have in our building envelope. Keeping our crawl space well sealed from the outside will also ensure that no contaminated air, earth gases or mold spores will infiltrate into the living space.

Roof Framing: Raised Heel Trusses

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.