Your Guide To Green

Sooner or later all the heat you produce inside your house will end up outside. The way houses are being built today, you need a supersized furnace to keep replacing the heat that is quietly sneaking out to play. How do you avoid this?

One way is to build your house airtight. This keeps the cold wind out and the warm air in. This may sound like a good solution but two important things are wrong with it.

First, this solution addresses only airflow. Your house also loses heat by other means.

Second, your airtight house will make you sick if you're not careful. Mold-producing moisture, stale air, and off gassing of chemicals from building materials and finishes, all get trapped inside an airtight house. Some well-meaning but misinformed people will tell you that you have to deliberately build your house "loose" so that it can breathe, just like an old barn. Building a drafty, cold house is not the 21st century solution.

Proper ventilation is key
The solution is to ventilate your house with a full-time, controllable, mechanical system, preferably one that recovers heat from the outgoing air. This is the only way to achieve high indoor air quality in your airtight house. However, this method is not required by code in most states, so your architect, designer, or builder will most likely not install it unless you ask for it.

Another way to avoid losing heat from your house is to insulate it well. Look at all those wooden studs in the walls, roof trusses on top of the walls, and joists in the floor. See the spaces between all of them? Almost all houses built today are insulated by stuffing batt insulation between all those members. But filling those cavities with something fuzzy will not stop a little airflow, let alone wind. The fuzzies will eventually absorb moisture and then sag, leaving gaps.

This is not good insulation, but its also not the real problem.

Take a second look
Take a second look at all those framing members before they're covered up by drywall. Think for a minute about what you see. All those framing members are...outdoors. They're cold. This is the real problem wrong with the way most houses are built.

Putting insulation in the cavities between them will not keep them warm. Each piece of framing is a thermal defect. Each board is warm on its indoor edge and cold on its outdoor edge, creating heat flow. As you heat up your house, each framing member attracts the heat from the interior of your house and conducts this heat to the cold outdoors. Heat doesn’t just rise. It travels from where its warm to where its cold, so your house loses heat through the floor just as it does through the walls and the ceiling.

Without proper insulation, your house will radiate heat to the great outdoors as long as you keep the furnace on.

Rigid foam insulation can be placed inside and out
The good news is you can have a house that keeps its heat indoors. You can do this by placing insulation outside the framing to keep it warm. Or you can place insulation inside the framing to keep it cold. In addition, you can include the traditional placement of insulation inside the cavities between framing members, but it is not a necessity if the insulation covers the inside or outside of the frame.

However, the insulation outside the framework cannot be fiberglass batts. It should, instead, be self-supporting rigid foam. This allows you to use any thickness you choose without wasting wood. (Traditionally if you needed a 2x4 wall but wanted to use 6 inches of insulation, you'd have to build a 2x6 wall, wasting wood.)

Now here's the payoff. The amount of insulation you use is not limited by the size of the lumber used in the framing, so you can use as much as you need.

How much insulation do you need? More than you ever thought. And you know you have enough insulation when your house doesn't need a furnace or an air conditioner. Or you can keep adding insulation to the design until a computer energy program predicts an annual heating bill of $100 or less.

Its pretty simple -- you want to insulate your house so much that it loses almost none of its heat. Then you can heat your house with almost any method. Why spend $15,000 on a green, super-efficient ground source heat pump when you can heat your house with a $240 toe-kick heater? Why spend $26,000 on a roof full of solar panels to power a heat pump when you can heat your house with the standby heat of a standard water heater? All this is possible if you use enough, well-placed insulation.

It also helps to build a small, sensible house, of course.

Find the right architect & builder for you
Many architects, designers, and builders will react by saying the use of that much insulation just isn't done or that it will cost too much. These usually are the same ones who will tell you that its okay to spend $15,000 on that heat pump but not on insulation. If they do, find another architect, designer and builder. There are plenty out there who know better.