OT: Superinsulation tip

When we built our house a year ago, we insulated the 6" walls with Icynene foam. We also tried a new trick and sprayed 10" of it on the bottom side of the roof before we sheetrocked the ceilings. We used no insulation over the ceilings. I just went up in the attic, it is 78F while it is about 100F outside.

Normally, an attic would be about 140-150F on a day like this and six inches of attic insulation would do a marginal job defending against it.

The next time you build something you really need to think about Icynene, especially foaming the underside of your roof. Our electric bill for this 3500 sq ft house runs about $200 a month during the hot months.

I agree. Our house attic is currently 140 degrees when it's 95 outside.

Massive Insulation is a worthy investment.. but not a lot of people want to pay for it.

By not blowing any insulation in over your ceilings you are now cooling that attic space with your air conditioned ceilings. If that attic is vented, and I assume it is it should be the same temp as the ambient air. The roof insulation prevents heat transfer from the roof.

Gordo

6 inches up on the under side of the roof would be fine to help keep the heat out but like others have said you are heating and cooling your attic and if you have vents in your soffit and ridge cap you are heating and cooling the outside world as well.


Put 10 to 12 inches on your ceiling and your light bill may go down to $150 a month for electric.

Gary

What you did is what's recommended. You no longer need attic venting, they can all be sealed off. This brings heating and air ducting into the heated/cooled area and there is less sweating.

I am building an addition to house, 26x38 garage with full story above that . Considering 6 in walls and spray foam walls , and vaulted ceiling with spray foam . What kinda money does the spray Insulation run ? I'm sure it'll bee worth it .

You are right. The foam insulation is the best by far. I wish I had done it. I still might do some more blow in insulation. I only have about 7-8" of cellulose in the attic with R-13 pink panther stuff in the walls, with vinyl windows.

I was told that that type of insulation is too tight and if used in a living space you need some kinda constant ventilating system ?

When we built, I used 2 x 6s 2' o.c. and 6" kraft faced batts in the walls. The ceiling has 12" batts. Make sure to get "energy" trusses that are built up about 8" at the top of the wall. Also include baffles in each truss space. We have lots of glass on the west wall, (more glass than solid wall) and at 3:30 p.m. it's still cool inside. We don't have ac. A westerly breeze keeps it cool once the sun goes down.

Larry in Michigan

Anytime you get the insulation up to superinsulation ratings and seal up the leaks to match, you need controlled heat recovery ventilation.

Its hard to retrofit, but superinsulation pays better than anything you can do to a house to control its energy consumption.

I'm not sure I like the Icynene product. The local vendor is hard to get along with, but I'm concerned that it prevents the encased wood parts of the struccture from breathing and so keeps them from drying and that can lead to rapid rot.

It also costs about three times per board or cubic foot of what fiberglass costs, and isn't the greatest R-value foam available but makes its claim to greatness on the fact it sticks to and seals all gaps that would be heat leaks in poorly installed fiberglass or foam boards. In fact that claim they make stronger than the real R value.

Gerald J.

Depending on the climate you need somewhere over a foot of ceiling insulation in most areas. approx 3X what you have in your walls.
I wonder how the shingles will hold up with the foam insul next to them ?

When we built here in N. Florida a couple of years ago (2300 sq. ft), we went with the spray-in recycled cellulose and good windows. The insulation has the same R value as fiberglass in the walls, but it is a "true" r value, it seals every nook and cranny. Then we put a bunch in a ventilated attic. We have been running around $160 per month electric (hot water on demand and stove/cooktop is lp, around $35 per month). In the spring and fall, electric has run as low a $50. I'm a big beleiver in this type of insulation.

When we built here in N. Florida a couple of years ago (2300 sq. ft), we went with the spray-in recycled cellulose and good windows. The insulation has the same R value as fiberglass in the walls, but it is a "true" r value, it seals every nook and cranny. Then we put a bunch in a ventilated attic. We have been running around $160 per month electric (hot water on demand and stove/cooktop is lp, around $35 per month). In the spring and fall, electric has run as low a $50. I'm a big beleiver in this type of insulation.

That's another valid objection to the foams, the shingles almost melt in the summer sun. They won't last long. May have to go with a metal roof to get it to last.

Gerald J.

In effect with superinsulation you pay for fuel savings up front. But as the cost of heating fuel has skyrocketed and shows no sign of slowing that insulation investment never looked better.

Gerald J.

I have found a couple objections to cellulose. First in this old house there are cracks between the window and door frames and the plaster or drywall. Winter winds (and summer winds) push cellulose powder into the house so all the dust is cellulose gray.

Then with time it settles and leaves gaps at the tops of the walls.

When retrofitted without a vapor barrier it gets wet and then is no value as insulation and speeds up the rotting of the walls.

Gerald J.

We put on mid-range GAF 40 year asphalt shingles. Before we did I contacted all the major manufacturers and none had any problem with what we intended to do. I don't think the shingles get any, or much, hotter this way. Most of the heat they experience is from direct radiation. Remember, with a traditional ventilated attic, the attic is still close to 150F. Modern shingles have to be able to stand up to extreme climates with margin to spare. The shingles should be fine.

We used insulated A/C ducts in the attic (putting the A/C outlets up high instead of trying to push cool air up from floor vents). And, yes, they do 'cool' the attic a bit, but there is less cooling loss than if the attic was hot.

Our attic is not vented, no need. The attic is a semi-conditioned space thus no condensation or mold problem. We don't heat or cool the outside. Our energy dollars stay in the house.

Makeup air is provided by earth cooling tubes, but really, whenever you open a door, use the fireplace, run a bathroom fan or the cooktop vent or the clothes dryer you are pulling fresh air into the living space. Our house never seems stale or stuffy.

As far as the wood not being able to 'breathe' and thus rotting early, rotting requires oxygen. A sealed piece of wood should last forever. Consider the shipwrecks where the lumber is at a depth where there is almost no oxygen in the water, the timbers are like new.

Yup, Icynene is more costly up front but won't get wet like cellulose, works better then fiberglass and you fix your cost at today's dollar more so than buying cheap insulation now and paying more escalating energy costs down the road.

We closed the house in during the winter. Without heat, just passive solar from the windows kept the place about 60F during the day and about 50F at night. The outside temps were around 30F at that time. Without running the A/C our place would stay about 80F on a 100F day. Not bad.