Help! Looking to finish bonus room over 3 car garage, however I am concerned about the “excessive heat” builld-up in the room. Here’ a few details: room is 14 x 36 with 5′ kneewalls & 8′ ceiling. 12/12 pitch roof. Insulation is R30 in ceiling and angle wall/ceiling formed by rafters. Vertical walls are R13. 1/2″ untaped drywall is up. The garage below has full insulation R30 & R13 and finished drywall. It also appears “excessively hot”. The roof has 12″ ventilated vinal sofit, asphalt shingles and full length ridge vent.
I know foam baffles were placed between the rafters durning insulation, but I still wonder if the excessive heat (and cold in winter) may not be caused by poor roof venting. How can I check this out and what can i do to rectify? Any other ideas?
Constructive comments are welcome.
Replies
What color are the shingles and which way does the surface of the roofs face.
The heat generated by dark shingles can overpower a whole lot of insulation.
A Great Place for Information, Comraderie, and a Sucker Punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
Shingles are "Charcoal Gray" (Black). ridge runs close to East/West
Most room over garages I've been in have seemed to suffer the same temperature swings-cold in the winter/hot in the summer. And these way less supposed R-value insulated than yours.
I have little help in answering your question but will keep an eye on this in hopes of hearing explanation and corrective measures.A Great Place for Information, Comraderie, and a Sucker Punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
I read an article that talked of relative reflectivity differences between e.g. 'white' shingles and 'dark' shingles. The difference was small. Conclusion was that white shingles buys you little protection from the sun relative to another color. The difference was only like 5 or 15% if I recall. It makes sense, too if you look at a shingle up close ... there really is no continuous/smooth surface for reflectance and a lot of the sun gets reflected off the granuals back down into the shingle. Shingles aren't really a good reflector.
Existing insulation is minimal. How deep are the rafters? Heat in the garage is likely due to the huge mass of hot air sitting just above in the future bonus room.
First and easiest thing is to check and make sure the rafter vents aren't blocked down at the soffitt. Seen plenty of times when FG batts were just stuffed into the rafter bay blocking the intakes at the soffitt.
If blocked, then you need to rearrange the insulation to unblock. If not blocked, you are probably looking at upgrading the entire insulation package. The details depend on existing rafter depth and of course budget. Good thing that drywall isn't taped, will come off much easier when you are ready to upgrade the insulation.
PLAIN AND SIMPLE, IF YOU ARE IN A HOT AREA THE ROOM WILL GET HOT EVEN WITH EXCELLENT ROOF VENTILATION AND INSULATION, PERIOD!
There is this magic device that most people use to get an interior cool in hot climates. And that is called an AC system.
I see that no one, including you has mentioned anything about AC for the space.
And of course you are going to claim, well I did not mention it because, like almost very new house, it has "whole house" AC "system". AND IT EVEN HAS A REGISTER IN THE ROOM.
What is never mentioned, but usually true, is that the the register is feed by 5 miles of 1" duct and does not even supply enough air to cool a small doll house. Nor is mentioned that there is no return vent in the room.
Am I getting WARM or HOT?
William the Geezer, the sequel to Billy the Kid - Shoe
AC? what's this magic you are talking about? We here in SE NC are still in the 1940's.
Where are you located? Helps to fill in your profile. If you have lots of unprotected south glass ... that could be part of the reason. What is the south facing characteristics of your garage? Got a pic? Your roof faces south. Do the garage doors?
Lack of attic venting will not affect the cold in the winter ... well it will actually keep you warmer, not colder. No, that doesn't mean elminate venting if it is there. Poor venting will increase heat in the summer, but not increase cold in the winter.
When I built my house I had FG batts in the attic rafter bays, the roof was vented with soffit-to-ridge vents. This was prior to me knowing much about insulation or thermal envelopes, yadda yadda yadda.
Same ole story, My attic was hot in the summer, cold in the winter. It was unconditioned storage space.
Several years later I finished the attic off into finished living space. I left the FG in place and put sheets of 2" polyiso insulation on the rafter faces and 1" polyiso on the gable end walls. I did this mid-summer.
The day I started the work, the max attic temp was 127 degrees. It took one day to install the polyiso. A day or two later the max attic temp was 77 degrees. And no, there wasn't a hot spell followed by a cool spell. It just has to do with how different insulations handle different types of energy transfer.
There's actually a little ditty in this month's FHB magazine that explains things in detail.
Adding more FG wouldn't have made a hoot of a difference. It's not always how much R-value you have. It's how effective the R-value you have is at doing what you want it to do.
Thanks to all for the comeback. The reason I have some reservations regarding heat and cold in this space is:
Example: throughout last night we had a pretty good rain storm, cooling things off fairly well. Early this morning the outside temp. was in the low 70's, this room was 82 and my walk around attic (uninsulated except for the floor/ceiling below) was 82. The garage was 91. Normally I find the bonus room to be about 10 degrees warner than the outside temp. 4 years of living in this house, consistantly shows this, plus it is great at retaining the temp. throughout the day (kind of like a thermous bottle). This does not seem normal to me.
As for the other questions, Location is SE NC near the beach. The Heat and AC is in but the duct to that space are not installed. As mentioned the ridge runs mostly east to west. The garage doors are on the north side and there are 3 Vellox (sp) skylights on the north side of the bonus room. Yes the skylights are operatable and include UV, argan gas and all the other things that the manufacturer recommended for this climate. the roof rafters are 2x10. All in place insulation is FG Batting
I think your reply/solution has merit. I did read the same article in the new issue of FHB but did not know how to compare the results to my situation. I do not relish the idea of pulling off the drywall. I have access to the space behind the kneewalls and will be removing some of the "horizontal" ceiling to revise the lighting etc. I'm not sure it would be a good idea to put ridgid insulation facing the unconditioned side of the walls. The 2x10 rafter space, except for the foam baffle is full of FG batts.
Guess I could leave things alone and over come the temperture swings with heat and AC. I have 2 guest bedrooms and a bath on the second floor adjacent to this bonus room (they share a common hall), same insulation etc. and notice it takes very little energy to climate control them.