Rehab or build new?

We narrowed down our options to two choices: either turning the garage into a house or building new on level site between the barn and garage. We think that building new is the wisest thing to do. Even though the bones and the structure of the garage could provide for a super cozy 1100 sq. feet of living space, building new will give us the layout and passive house credibility we’re looking for.

I do understand that rehabbing an existing building on the property reuses the embodied energy already present in the structure and creates less of an impact on the land. So we will take full advantage of this by making the garage a bakery, a kitchen, or a farm store. It is close to the road and is easy to access.  

Here’s an early draft of our passive house layout:

20x40-passive-house

Passive House building notes:

The foundation will be a monolithic or slab-on-grade foundation that should have close to a R-34 insulation value. Walls will be insulated to R-45 and Roof to R-62. The goal is to create an airtight building envelope with very low thermal bridging.

Passive House is a performance-based building standard that can result in a house that consumes as little as 10% of the total heating and cooling energy used by a house built to the 2006 building code. – Finehomebuilding.com April/May 2010

DIY Prefab Insulated Panels

After the slab is set, I will build a post and beam (load-bearing) structure and seal it with DIY insulated panels for the roof and walls. These insulated panels will be a sandwich of either blown-in cellulose or recycled cotton insulation with XPS foam boards towards the exterior. The panels will be thick, at least 12-16″ in depth. But it’s this large amount of insulation coupled with an airtight envelope that will reduce our heating and cooling needs drastically. Insulation is a fixed cost that I’ll spend more on now with the hopes that I’ll need less energy to heat and cool as those costs continue to rise. After a century of blowing heat into thin-walled homes, the passive house standard in our colder, northern climate makes a whole lot of sense.

They will have pine tongue-n-groove boards on the inner side making up the finished interior wall covering. No sheetrock is going up in this house! These panels will have the rough window openings and electrical cut-outs as the plan dictates.  What I’m going for is a prefab panel concept that anyone could easily replicate after the timber framing is up.

Heating & Venting

The house will be facing South with triple pane windows on that side to maximize solar gain. Our heating needs should be adequately taking care of with a small wood stove. Several zones of radiant floor heating and a heat pump designed for cold climates will suffice for when we are away for an extended period of time in Winter.