spray foam insulation and its effect on roofing/venting


Old 05-29-08, 08:22 AM
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spray foam insulation and its effect on roofing/venting

We're gutting a 70 year old house and have replaced the roof with 50 yr shingles. On the interior, the 3rd floor rooms have sloped ceilings, so the attic essentially has 3 areas (a small cathedral ceiling attic, and two triangular floor level attic/storage areas with soffits).

After a lot of differing opinions from the building inspector, the environmental assessor, the 4 various insulation companies we had contacted to get quotes, the HVAC mechanic, we were to understand that venting wasn't an issue and that we didn't have to worry about putting in an HRV system. We have been told that in order to benefit from the superior insulation and get max. R factor, we should spray insulate from the header space on the 2nd floor up to the top of the cathedral, in between joists. This would cover the soffits.

However, we now understand from the roofing shingle manufacturer that unless the attic is properly vented (i.e., the soffits are not covered by the insulation), they won't guarantee the life of the shingles.

I'm at a loss to figure out how to address the roofing ventilation and whether or not it's required. Can you offer any advice?
Old 05-29-08, 11:54 AM
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Given the age of your house, you should determine whether or not you have stopped soffits. That is, see if the soffits are open at the eaves to the outdoors. Stopped soffits are somewhat common in the construction of older houses. Mine is the way.

If the soffits are stopped or blocked because of the construction of the house, ventilating the attic will have to be achieved by gable end vents and ridge vents or something along that line. I don't know if you have a gable roof or a hip roof.

If your soffits are open, then venting channels can be installed that run from where the top of the wall approaches the roof so that they run along the roof to the point that the insulation is kept away from the underside of the roof. This assumes that there are also soffit vents in sufficient number.

Having made these determinations, the installation of the insulation should be straightforward.
Old 06-22-08, 08:08 AM
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50 Year Shingles??? And no ventilation??

The Shingle installer is responsible for ensuring proper ventilation. These days, it's not just about the shingles. It's about surface prep and ventilation that makes the 50 year shingles last 50 years.

Without proper prep and air flow under the surface, they will last as short as 5 years... or one winter.

If the installer skimped on this, I'd bet they forgot snow/ice shield and proper flashing too.

Now.. If the roofers did proper ventilation, and you're thinking of spray foaming, there are plastic forms you can place between rafters to maintain ventilation. I'm amazed the spray foam guy didn't mention this.

They shouldn't spray foam over the 'side of house' soffit vents. It's all about preparation before the guys with the guns show up. Only the CEILING of the 3rd floor room would need spray foamed so it shouldn't cover the eve vents.

In short, you'll need to vent and insulate along the roof up to the ceiling of the 3rd floor (venting from the soffits up to the 3rd floor ceiling), then insulate the ceiling of the 3rd floor.

You might need to tear out the sloped 3rd floor walls to do this. This is the tough spot.
Old 06-23-08, 02:58 PM
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My shingle mfg (Elk) makes exceptions for certain foam products and sealed attics. There are lots of benefits to this different approach. Ask your shingle manufacturer about the specific spray in place product you are considering. The ventilated attic requirement is for standard insulating materials.
Old 07-03-08, 05:02 PM
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Insulation Needed

Our home was built in 1910. The roof is metal and painted. Initially, our contractor suggested using hydrostop ( a rubber polymer that covers the roof after it is cleaned and lined with a thin membrane cotton material which absorbs the polymer) thus making the roof an insulating device. The roof is then painted again, the same color as before. Our roof is red and is less than 10 years old. A friendly neighbor informed us of this after watching us angst over what to do about the roof and watching me actually climb a ladder and take photographs of the roof.

We thought it was leaking. It was not. A square had been sealed that used to allow for old 2 story homes an escape route and it was leaking. We fixed it and except for the poor insulation and discoloration of the roof, we do not have "roof problems" - So do we "re-paint the roof along with the rest of the home?

We live near a river and the east coast in NC.
1. Paint type?
2. Insulating material in the attic? The beams are very close together and not wide enough to use the roll-type insulation if we wished. We do not.
3. As our home is historic and old, we are supposed to get prior approval for repairs. Our windows are original with the weights and pulleys and as we begin to repair we wish to use foam for insulation around the area in the walls. Most of the glass needs to be re-glazed (we did not know due the thick paint) prior to our moving in.
4. Our home is made of wood and the people we purchased from used inferior replacement wood for repairs.
5. Although the paint job looked fantastic, it is crumbling now. They did not use a primer coat.
6. The list goes on, but for now, given the information above, and that we cannot use storm windows. How do we insulate as our utilities are outrageous?

It does not help to learn that our home was purchased to "flip" one year prior to purchase and that we hired 2 independent inspectors who marveled at the workmanship and beauty of our old home!

Any ideas?

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