Thread: Attic Temperatures...

It's been quite a while since anyone has posted on the issue of attic temperatures. Is that because the issue has become less prevalent these days due to the increased use of attic temperature reduction products? I have been keeping a log of attic temperatures in AZ, CT and NY. I am looking for as many current datapoints as I can get. In as many states, in as many months (throughout year not just summer) and under as many conditions (type of roof, etc) that I can. The existing data on this is very sparse. I would actually like to create a database. Any input on what you are finding out there would be great. Thx!

Similar Threads:

• Attic access problems
• Attic painted
• Hi/Low vents terminate in the attic?!
• Short Attic Ladder
• Protection of wiring in the attic

Originally Posted by George Luecke

It's been quite a while since anyone has posted on the issue of attic temperatures. Is that because the issue has become less prevalent these days due to the increased use of attic temperature reduction products? I have been keeping a log of attic temperatures in AZ, CT and NY. I am looking for as many current datapoints as I can get. In as many states, in as many months (throughout year not just summer) and under as many conditions (type of roof, etc) that I can. The existing data on this is very sparse. I would actually like to create a database. Any input on what you are finding out there would be great. Thx!

I do not take random temperature readings of the attics I inspect. I do know that during the summer months attics in my area will hit 130f without any trouble. Once they get that hot I do not spend much time in them!

Interesting idea George. I have wanted to do something like that for years but never got around to it.

I happened to have my infrared therm. with me recently and took the following readings.

Location:Las Vegas, NV;single family, ranch style, home; south facing; reading of decking was south roof field; roofing material asphalt/fiberglass 3 tab shingles, one layer; approximately 10:30 A.M.; outside temp about 99 degrees.

I don't know what the air temp was in the attic but I didn't stay there very long either!

Originally Posted by Dom D'Agostino

The post is a spam from a "energy" company that sells roof/attic vent products.

Posted in the Roofing Forum as well.

I was in one last week and it was 189, let me see if I can find the pic.

179. How the heck do you down load the IR pics.

Originally Posted by mathew stouffer

179. How the heck do you down load the IR pics.

With a pot holder

Hello,

I use the rule of thumb that the attic should not be hotter than 20°F above exterior ambient conditions. I consider the attic venting to be under-performing above that. If I remember correctly that rule was given to me by Air Vent Inc. at a seminar.

Damon

I agree with Bob. I will look for my photos as well but I also have recorded the 180 degree (upper) range in the attic when there has been very little wind movement and exterior temperatures exceed 115 degrees. No, you won't stay up there for long, and yes (Damon) the ventilation is sufficient. Your thought process is correct for Oct, through May in our climate. But Las Vegas has a dry heat so it only feels like 112 in the shade. The majority of the roofs I inspect are concrete tile, 20% are composition, and 5% are rolled built-up with no attic access (Town homes). The percentages are rough estimates.

Putting a data base together for this kind of thing might be useful, however, there are so many conditions to consider beyond what has already been mentioned. I don't see any mention (other than one poster) regarding roof material type or types, color of roofing material, surrounding growth and shade, surrounding structures that might affect outside airflow, etc....

Various energy audit softwares do this based on years of data gathering and inserting all these considerations into the software calculations to arrive at recommendations and conclusions. Not sure if a chart made from data bases would be of real value.

135 is common for me.

Originally Posted by Damon Sagehorn

I use the rule of thumb that the attic should not be hotter than 20°F above exterior ambient conditions. I consider the attic venting to be under-performing above that. If I remember correctly that rule was given to me by Air Vent Inc. at a seminar.

Damon,

I wonder where they got their 'rule of thumb' from?

Rarely would I see an attic which was only 20 degrees warmer than exterior ambient during the summer. During the winter, yes, but not during the summer.

In South Florida the typically daytime temperature might be 92 degrees to 95 degrees and the attic temperature might vary from 120 degrees for a tile roof to 140 degrees for a dark color shingle roof.

I doubt that any reasonable amount of natural (non-forced) ventilation would keep the attics within 20 degrees of ambient during the summer in many areas around the country. And using forced ventilation creates its own problems.

Attic temperatures, geesh... wrong month for me. It's hot and there are certainly hotter places

I have shot some temps near 160, but not 180... wow!! That's HOT. I try to remember and carry a box fan for my PM appt's. They are nice to have in the kitchen, whilst I type in data!!! Doesn't it always seem that if you have a 4pm appt on a 100 + deg day, the AC isn't gonna be working???

On somewhat the same topic, I had a HOT ONE (I was sweating) the other day and a client asked me about Powered Ventilators and had some thoughts:

Curious - You are performing a Home Inspection, you enter an attic that is BOTH well ventilated and just too darn hot. Does one mention powered ventilators? At some point a customer is likely to save additional $$ on their cooling costs by lowering temperatures in the attic.

But, where does this become a benefit? For example, we enter the same above mentioned attic at 180 degrees, the attic is reasonably well insulated and so are the flex ducts (say 9 inches of batts and R-6 ductwork) I "know" that a customer would benefit or save $$ on operating costs by significantly lowering attic temperatures in this scenario when they are keeping the home cooled to say... 72 degrees.

There is certainly less benefit if we look at the same example above and reduce the attic temperature to 130 degrees and reduce the cooling load to an interior temperature of say 78 degrees.

Is there a Matrix or Table that anyone has seen in relation to these types of scenarios?

There are many dis-advantages to powered ventilators in both the forms of a whole-house fan as well as a powered gable fan, I'm aware of most.

Originally Posted by Tim Spargo;142005
Curious - You are performing a Home Inspection, you enter an attic that is BOTH well ventilated and just too darn hot. Does one mention powered ventilators? At some point a customer is likely to save additional $$ on their cooling costs by lowering temperatures in the attic.

But, where does this become a benefit? For example, we enter the same above mentioned attic at 180 degrees, the attic is [U

reasonably[/u] well insulated and so are the flex ducts (say 9 inches of batts and R-6 ductwork) I "know" that a customer would benefit or save $$ on operating costs by significantly lowering attic temperatures in this scenario when they are keeping the home cooled to say... 72 degrees.

There is certainly less benefit if we look at the same example above and reduce the attic temperature to 130 degrees and reduce the cooling load to an interior temperature of say 78 degrees.

Is there a Matrix or Table that anyone has seen in relation to these types of scenarios?

There are many dis-advantages to powered ventilators in both the forms of a whole-house fan as well as a powered gable fan, I'm aware of most.

I can't give you empirical data but in my own experience I quit using or recommending power ventilators after seeing the deplorable rate of failure of the motors in these units.

In my area they do well to last more than two summer seasons.

Also, you are paying to drive a fan with electricity to cool an attic by a very marginal amount (trust me they do not make much difference) which also will tend to depressurize the attic causing more air leakage from the interior of the home.

Bottom line for me is they do NOT save energy in the vast majority of installations, in fact if measured I would hazard to guess there would be a net cost in energy, not a savings.

Maybe in isolated cases one could make a good argument for the installation for problem areas but think about it, you have a heat engine just waiting to do work trapped up there in the attic.

Just cut a hole and let the hot air rise. The greater the temperature differential, the more power the heat engine has and the greater the ventilation rate.

I much prefer balanced passive ventilation, preferably continuous soffit and ridge vents and you have a very efficient attic with no electric cost or moving parts to wear out or break.

Then throw some radiant barrier on the bottom of the roof decking and some insulation for good measure.

Originally Posted by Tim Spargo

Does one mention powered ventilators?

Yes, if there was a powered attic ventilator I would mention to my client that it was a GOOD THING the motor was froze up and not working (see Jim's comment about the high rate of failures for those motors) because the main thing they do is suck the air out of the attic and depressurize the attic relative to the living space inside the house below, thereby sucking the a/c and everything else up through all the unsealed openings we all know are supposed to be sealed but are not sealed, and sucking out more than they will save, and, to make the matters even worse, that has now depressurized the house, which now must take in even more air from outside, air which is hot, humid, etc., and air which now needs to be conditioned.

I had a powered attic ventilator on our house in South Florida, but after attending a couple of Dr. Joe's classes I disconnected it and quit using it (even before the motor had a chance to go bad). Power vented attic, whether blowing in and pressurizing the attic or sucking out and depressurizing the attic, are bad for the living environment in the house, and probably equally bad from an energy standpoint.

Jerry and Jim,

Thanks for the replies and info. Much appreciated.

Originally Posted by Tim Spargo

Jerry and Jim,

Thanks for the replies and info. Much appreciated.

I like the solar vents. They don't run at such high speeds and depressurize the attics and keep a gentle draw going as long as there is daylight.

Electric vents I bash all the time. Just the hole in the roof the size for those fans is better than running that fan.

If you have a long ridge or multiple ridges to add ridge vents I favor ridge vents all the time as long as there is adequate eve vents. I have always been in favor of the 4 inch slot around the entire home in the eves for vents with ridge vents.

Originally Posted by Ted Menelly

I like the solar vents. They don't run at such high speeds and depressurize the attics and keep a gentle draw going as long as there is daylight.

I have not had much experience with solar vents except that the ones I have priced were about $200+ each and most houses would need multiples. I figure anything with an air cooled electric motor is going to roast and fail in Texas.
I still like the heat engine that is naturally present in every attic. Just cut some holes in the right spots and let it go to work. And it still works at night or cloudy days. No maintenance, nothing to break or wear out; well you might have to brush the screens off on the soffit vents or replace them if they get clogged with paint.

Originally Posted by Jim Luttrall

I have not had much experience with solar vents except that the ones I have priced were about $200+ each and most houses would need multiples. I figure anything with an air cooled electric motor is going to roast and fail in Texas.
I still like the heat engine that is naturally present in every attic. Just cut some holes in the right spots and let it go to work. And it still works at night or cloudy days. No maintenance, nothing to break or wear out; well you might have to brush the screens off on the soffit vents or replace them if they get clogged with paint.

I must admit that the oldest one I have seen so far was 3 plus years and still quietly turning away. The only reason I new the age was because the folks had the paper work from the installation date. I have seen them just installed and the 3 plus year old unit appeared to be running and looking pretty new and acting as though it was new in comparison.

If in fact the units do not fry for years down the road then they will be the way to go.

Originally Posted by Ted Menelly

I like the solar vents. They don't run at such high speeds and depressurize the attics and keep a gentle draw going as long as there is daylight.

Originally Posted by Ted Menelly

If in fact the units do not fry for years down the road then they will be the way to go.

Those still depressurize the attic, just not as much, thus they still have a negative impact on the living space similar to 120 volt powered exhaust fans ... just less of a bad impact.

Saying that they are the way to go is like saying that, because cutting your finger off does not hurt as much as cutting your hand off, that cutting your finger off is the way to ...

Originally Posted by Jerry Peck

Those still depressurize the attic, just not as much, thus they still have a negative impact on the living space similar to 120 volt powered exhaust fans ... just less of a bad impact.

Saying that they are the way to go is like saying that, because cutting your finger off does not hurt as much as cutting your hand off, that cutting your finger off is the way to ...

Jerry

Very minimal impact and built to such. It is meant to be a low steady draw thru the attic up thru the eve vents. No, not like a high revving impact like a power fan. The depressurization would be very little to none.

As far as it is the way to go "If in fact the units do not fry for years down the road" then they will be the way to go" Long lasting, steady mild flow of air thru the attic instead of hot, dead, humid air slowly making its way thru the roof adding higher temps in the attic, no economical impact in everyday use like the electric fans.....Why would it not be the way to go. I did a smoke test on one. They are nothing like turbine vents that spin like hell but do about no drawing up thru them. Hold a cigarette under a turbine vent and you will see the smoke swirl around for a long time before vent up and out. Do this to a electric vent it will suck the cigarette out of your hand. Do it to the solar vent and it has a light gentle draw that does nothing to pressurize a home thru leaks to the attic. I would put it at about the same as a breezy day that always keeps an attic cooler and no more. I am not talking felling the breeze either. Just that klittle extra draw to hols the temps down.

Why would I not say that if I have experienced all many times. It is my opinion and I believe a very well rounded one. May I not have an informed opinion?

As far as your saying lately like saving the life of a convict to kill him and then the one above Are you having serious scary nightmares lately

Oh yeah...in case I forget....I don't smoke, I borrowed the cigarette.