Hi,
I am planning to add a room to my existing home. I plan to/am thinking I would like to give the room some height and feeling of openness by having the sheet rock ceiling follow the roof/rafter lines (vaulted ceiling). I have lived in a home with such celing before.
Today, the common technique that I am familiar with is to put in the R-30 bat fiberglass insulation but be certain there is at least two inches of space between insulation and roof plywood to allow for soffit to ridge ventilation. Recently, I have read severl articles endorsing simply spraying the interior celing with foam insulation -that will stick to the rafter and roof plywood and then, after cleaning off any excess foam, attach the sheet rock to the rafters. One article said, the foam would eliminate the need for roof ventilation. This sounds a bit off for the southeasterna and southwestern states where heat build up is high?
Is this logic valid for south central Texas and Central Louisiana?? Living in these regions of the country, I have been told the ventilation of attics and roof spaces is critical not only for reducing heat load into the living space but to reduce temperature build up in the roof itself. I have read articles from the “experts” that indicate the heat build up can lead to premature failing of asphalt shingles. I have also seen the roof shingles on the side of my house catching only the afternoon sun seem to deteriorate faster than the side catching the morning sun.
Any thoughts would be welcome, and being the reading type, citations for relevant articles/books would be welcomed.
Take care,
Cal
Replies
Greetings Cal,
This post, in response to your question, will bump the thread through the 'recent discussion' listing again which will increase it's viewing.
Perhaps it will catch someone's attention that can help you with advice.
Cheers
We all like this way here. Strapped, meshed, and blown 'glas (Johns Manville)
http://forums.taunton.com/tp-breaktime/messages?msg=84041.233
Nice space now
http://forums.taunton.com/tp-breaktime/messages?msg=84041.331
Forrest
Is this logic valid for south central Texas and Central Louisiana??
Foaming the roof deck and over the rafters? You bet.
I'm between the Brazos and the Navasota rivers--it's humid and bottom land all over.
By ventilating the roof, you are letting in damp air allegedly to flow over the roof structure, which will then cool that structure. In actual practice, it works jsut as well as leaving the windows on your car cracked open, around 4-5º difference.
So, the attic in a ventilated house will only run 130-135º and not 135-140º.
More ciritcally, for about a third of the year, the cooler third, a ventilated roof is admitting damp air which can then condense on any surface at or below DP.
I'm still collating the data (as we have had a bit of a "moving target" in the recorded data). Where we retrofit foam to R30, and 1 to 1.25" over all roof framing. Peak recorded attic temperature was 84º Now, if the a/c settings had remained constant, we'd have a better performance graph. But, as the outside temperature rose, the a/c was working with ductwork much closer to "room temperature," which made it easier to reach the temperature settings on the stat. Which was actually a tad under-need for dehumidifaction, so the stat settings kept being adjusted lower.
Winter performance showed no real change in utility usage.
So, this is not voodoo, just new, and new thinking, somewhat.