Reducing attic temps
I have a door accessible attic space over living area. It’s floored. There is blown cellulose insulation under wood floor (maybe 8 or 9 inches). The attic roof is shaped cathedral or A frame style.
There are vents every few feet at the edge of the roof (soffit vents?), a ridge vent and a new gable exhaust fan installed by me on the recommendation of the Home Depot guy which basically did nothing to lower the temperature in the attic.
Since the fan utterly failed to lower the temp, I’ve spent a lot of time now reading about radiant barriers, foam boards,etc. The cheapest and (if you believe the hype) miracle product seems to be these foil radiant barrier products from places like attic fowl (changed the name in case trademarks are disallowed – no dis intended). Would this be my best bet just to try to keep attic temps down to the ambient outside temp? Assuming it is installed across the rafters leaving that 6 or 8″ space between the radiant barrier and the roofing plywood?
Would the r-max or r-tech foil faced foam board be better? Attached again across the rafters? I see no claims about r-max or r-tech foam boards being a radiant barrier even though they are shiny foil faced.
If I install the r-max/r-tech, do you leave room at the bottom and top of the rafters for ventilation channels up through the rafters to the ridge vent like you do with the foil?
I’m worried about moisture as there is a bathroom that vents into this area (was like that when we bought it last year). There are no HVAC systems or ducts in this area. It’s just unused space I would like to safely store items without baking them or turning things into puddles. I want to do it myself (I’m handy) and I don’t want to spend a fortune if it can be helped. It’s doesn’t need to be a NASA clean room where I can build a lunar module.
Location is Chattanooga, TN. climate zone 4a
Thanks for taking the time to read this and hopefully offering advice.
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Replies
First thing you need to do is get that bath exhaust venting out through the roof or a soffit. It has no business venting into the attic - that is really bad for your house, even if it was like that when you bought it.
Second the attic will be hot, but you should check to be sure your ridge vent is not clogged. Check from inside and outside. Then check to be sure the soffit vents are not clogged from insulation over into the soffit.
Then realize it will always be MUCH hotter up there than anywhere else and you only store things up there that can get hot without being damaged.
Fiberglass insulation is cost effective and doesn't prevent the roof from drying into the attic.
The best use of attic storage space, if the attic is hot, is to fill it with insulation and keep the heat out of the house. Then maybe get a shed for storage. I realize that doesn't work for everyone but it's worth considering.
Do not vent a bath fan to a soffit. Out the roof or out a table end.
Tom, can you explain what a table end is? I'm not familiar with that term.
Gable end. Autocorrect in action.
Thank you
Thank you everyone for taking the time to respond. I appreciate it. I will schedule someone to run the bathroom vent to the roof.