Saturday, May 21, 2011

My Next House Will be Superinsulated...

I should be painting and wallpapering, but daylight is already gone, so I better not. Instead, I'm jotting down my thoughts on insulation vs energy efficient heating techniques.

Since we moved into this house, I've spent a lot of time to figure out how to make it as energy efficient as possible. Plenty of insulation must be by far the easiest way. However, no matter how much we add to the walls and roof, the basement floor will always be a heat sink. And how do you insulate an existing basement floor (concrete slab without any insulation under) when the ceiling hight is barely enough as it is. That's where I get stuck.

Lowering the utility bills is a very strong driver. Those bills will only be more expensive with time and probably increase a lot more than inflation. However, "alternative" energy for heating the house is also costly.
- Geothermal heating/cooling - extracting heat from the ground means drilling or digging up the entire yard and buy a new furnace.
- If we installed more floor heating, it would be efficient to use solar heating since the water temperature is quite moderate. After all, we have a large south facing roof, ideal to harvest the sun's energy. But what is the price tag? However, I believe manufacturing, transportation, installation, maintenance, repair, raw material etc. consumes quite a bit of energy for an advanced high tech system. How long do I need to use it before it has created as much energy as was put into it? The recovery of that energy need to go into the total environmental balance sheet as well.

So, I've started to dream about my next house. After all, in only 10 years, all three kids will most likely be off to college and it might be time for another project...

An article in the Chicago Tribune this winter really pinpointed the idea of superinsulated, passive or zero net energy house: Insulate like crazy and then a bit more, and you won't need a lot of expensive technology to heat or cool the house. The energy bill for a passive house is negligible. You only need a ventilation system that recovers the heat of the outgoing air. Sounds simple and with simple, there are fewer things that can go wrong. Almost the entire industry for alternative energy sources will be bypassed (for the purpose of heating/cooling houses and buildings).
Two studs would have been
plenty for this little window.
Earlier today, I tripped over the term "Larsen Truss" and had to look it up. It's a way to build a superinsulated house with no more lumber than you would use in a standard 2x6 framed house (!). With two layers of 2x4 studs, interconnected every so often, thermal bridging is also minimized. The other trick is that the sheeting is omitted. It is a clever mix of balloon and platform framing.  Here are description, pictures and comments. I understand that it is very unusual not to have sheeting in the US, but that is the standard way of building in Sweden, so I would think only tornado and earthquake prone areas would need it here. Is it a coincidence that a Scandinavian name is associated with this framing technique...

The triple studs under all our new windows is one of the few things I would have liked to do differently. Unfortunately, I wasn't fast enough to react when the builders framed the new outside walls. Apparently two studs are a must according to the building code. Especially, a small window like this does not need that much lumber. It just increases thermal bridging and makes less space for insulation.

I would LOVE to have deep window niches like we had in Sweden! Including everything from siding to drywall, those walls were about 12" thick.

No comments:

Post a Comment