I went by a house renovation the other day. They were doing all sorts of fancy stuff – especially a super high end radiant floor heating installation. And then they were putting in 3 1/2 inch fiberglass insulation for the exterior walls.

From the perspective of a green brownstone builder that’s like ordering a really expensive meal and garnishing it with ketchup packets you stole from McDonald’s. You wasted your money since it’s just going to taste like fast food anyway.

And the same goes for them. Radiant floor heating saves money because you don’t have to heat the house as much. But their utilities are still going to be higher than necessary because they are throwing away all the great heat from those expensive radiant floors through badly insulated walls.

The contractor on the job knows what he is doing and by all “normal” standards he is doing a great job. He is doing everything right. But he is building by non-green standards.

Non-green standards are about comfort in a world where fuel is cheap and America is great. Those radiant floors will feel great under foot. The client will be happy and compared to the previous house that had bad insulation WITHOUT radiant floors he might even see his utility bill go down a bit.

But green construction standards require MUCH more insulation and have much higher expectations towards lowering fuel bills.

My rule of thumb is to insulate by your latitude. Brooklyn is at 40 degrees north. Thus your Brooklyn brownstone’s exterior walls should be R40.

That’s a lot of insulation.

But what’s cheaper, three thousand dollars of insulation now or ten thousand dollars over the next ten years? As anyone who feels the clock of time ticking will tell you, time flies. Don’t invest your money in your utility bill. It’s really a crappy way to save for retirement.

Fiberglass takes up too much space so you have to go with PolyISO if you can find it recycled. Otherwise dense packed cellulose is good but still takes up space. If you don’t have qualms about using so much fossil fuel and have money to burn then spray foam is also great. If you really have money to burn then you can used cotton batts.

The way we are doing the Brooklyn green show house is with three sheets of R9 poly ISO. Each sheet is 1.5 inches thick so that is 4.5 inches of insulation with a total R value of 36. There are 12 inches of brick but that has minimal R value. This site says that each 4 inch brick is about half an R value so 12 inches would be R3.

That makes our walls R39.

But we are also doing a radiant aluminum foil heat barrier which doesn’t add R value but does stop heat (I know, that sounds strange).

In cold climates you want the foil to be on the inside of the house just behind the sheet rock. That way it radiates the heat back INTO the house. In warm climates you want it just behind the outside siding so it radiates the heat AWAY from the house.

One issue with radiant heat foil is that condensation can form on the cold side of the foil. That is in the wall and can cause mold issues. But in a super insulated house that issue is greatly reduced since the heat difference on each side of the foil is minimal.

If the house wasn’t insulated there would be a big difference in temp on each side of the foil and just like a glass of water with ice “sweats” so would the foil.

Another crucial issue with the foil is that it needs at least half an inch of air on one side of it. Otherwise it isn’t able to radiate the heat back and it actually becomes a conductor of heat and as you know metal is a great conductor of heat.

The foil is NON-perforated, meaning it has no micro holes in it that companies put into it so that it breathes. Non-perforated foil also doubles as a vapor barrier. We don’t need it to breather since we are supper sealing everything. The plan is for no humidity to get in there in the first place.

You either build to let things breathe (with natural materials like clay for example) or you don’t and you have to be damn sure which way you are doing it. If you mix the two styles you have serious humidity issues.

Along the same lines we put tar paper in the mix to seal the wall even more from the elements.

And one last thing. Normal construction calls for insulation to be put BETWEEN the studs. This is like putting on a nice warm jacked that has strips cut out of it. Those strips are going to feel cold if you go outside.

The studs are also pretty good at passing cold through. Wood is an ok conductor of heat. Metal studs are great conductors of heat.

So to break that we put insulation sheets BETWEEN the studs and the brick wall. Or we put it OVER the studs. Or we do both. Basically we mix it up because we’re still exploring the best way. But the bottom line is that there is nowhere where cold can pass through any hard surface all the way from the outside to the inside. It will always eventually hit insulation.

First we seal up the bricks really well with cement. They have had a hundred years to deteriorate so the cement seals cracks and strengthens them. Sealing cracks is VERY important because you want everything air tight.

Then we put the tar paper on. This stops any major leaks. We tape and caulk it to make it a vapor barrier of sorts. The tar paper is dunage. Dunage is material that is damaged and the store can’t sell. So instead of throwing it out they give it to me or sell it for pennies on the dollar. They are happy to be rid of it without paying the dump truck to remove it.

Then we put a layer of insulation. The insulation is salvaged from another building.

Then we put the studs. They are salvaged wood that we cut down to size. We also foam seal any large gaps in the insulation. Other times we use tape. We cut the insulation to size and pack it in tight to minimize air holes.

Then we fill the studs with insulation.

The studs are half an inch thicker than the insulation so that when we put the insulation between the studs, the studs stick out half an inch. This allows us to put the foil over the wall and it creates an air space of half an inch.

Then we put the sheet rock over that right at the end. We caulk the sheet rock and paint it to form one final seal.

These walls aren’t letting in ANYTHING!

The temperature in NY changes steeply day to day but inside the house the temperature will remain steady. The insulation will keep us insulated from the swings of temperature. The heater will hum along at a low setting and never really have to move up or down. Of course to make up for the super sealed walls we will need to ventilate the house. We can’t rely on normal house cracks for it to breathe.

But that is a whole different story….