Reducing the heat build up in the attic

3,271 Views | 17 Replies | Last: 4 yr ago by evan_aggie
Ferg
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Last year I had to replace an Air Conditioner and the vendor gave me an estimate and recommendation on what it would cost to reduce the heat in my attic.

They recommended a solar vent with a fan vs the regular vent i have, as well as more insulation in the attic (unfinished) floor, and spray on radiant barrier.

I'm thinking about doing something later this year, but not sure about which of the above.

The insulation seems like a no brainer, but I don't know about the other two.

Has anyone had any experience with them, and based on that what do you recommend?
(Also, does a radiant barrier impact your cell signals?)


Thanks
Scruffy
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AG
I'm not a home builder, and all my experience outside of drywall has been commercial work excluding a few odd jobs.

That said, in my current "semi-retirement" I've been watching a lot of Matt Risinger videos on youtube:
https://www.youtube.com/channel/UCFCTrfb1JUJjs3Im8OZDtBw

He seems to have the idea that venting the attic is not a good idea in Texas (he's out of Austin) and instead a better idea is to condition the space. Seal it off and maintain a comfortable temp. The reasons he lays out seem reasonable, and maybe a builder on here can chime in, as again I don't know anything other than what I've watched.

If I remember, on one of his videos, he talks about the idea of roof vents to help cool the attic space, and his point was along the lines of while you might bring it down from 140F to 120F, you are still just keeping the space hot.

Hopefully someone in the residential trade can chime in, as again I don't know much on that side (or on any side period) and while everything on the internet is true...I don't know how true it all may be.
Vernada
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AG
I had a solar fan + soffett vents in my last attic. It worked well. Attic temp stayed pretty close to ambient - which was a huge improvement.
BrazosDog02
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AG
I agree with him but this is one of those things that can be stupid expensive and come with a good chance to completely Pho ck up your building envelope if done improperly and create a host of collateral issues.
Whoop99
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AG
If you have soffit vents, take them down and hose them down. The mesh was completely clogged on my vents, preventing good air flow into the attic. Also, make sure that the builder actually cut holes to match your vents. I had several that had openings only about half the size of the vent. I used my jigsaw to match the openings to the vent size. These two items definitely helped the airflow in my attic and didn't cost me anything (this assumes you have a the necessary tools already).
Gig 'Em,

Whoop99
The Fife
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Ferg said:

Has anyone had any experience with them, and based on that what do you recommend?
(Also, does a radiant barrier impact your cell signals?
In our houses fans of any kind were largely ineffective. Radiant barrier made a huge difference on the other hand. There was no noticeable impact to phone signal.
Ferg
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The Fife said:

Ferg said:

Has anyone had any experience with them, and based on that what do you recommend?
(Also, does a radiant barrier impact your cell signals?
In our houses fans of any kind were largely ineffective. Radiant barrier made a huge difference on the other hand. There was no noticeable impact to phone signal.
Did you get it sprayed on?

Also, no impact on wifi within the house?
Aggietaco
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AG
One thing you have to remember with Matt (he's a friend of mine), he's only interested in new construction these days and a lot of his ideas apply well to the multi-million dollar homes he builds with thought out plans and spec books and not so well to the rest of us. A conditioned attic is one of those things that needs to be planned before your home is constructed, it doesn't work as well for a retrofit.

The best course of action for those of us with traditionally built attic spaces is to keep the air flowing from the soffits to the ridges and keep a nice blanket of insulation between the conditioned space and the attic. There are a number of ways to do both of those and the right answer depends on your individual home.
dubi
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AG
Vernada said:

I had a solar fan + soffett vents in my last attic. It worked well. Attic temp stayed pretty close to ambient - which was a huge improvement.
Mr Dubi installed lots of soffits and a thermometer controlled fan in our A-frame style rent house. The attic was probably 25 degrees cooler afterwards.
The Fife
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Ferg said:

The Fife said:

Ferg said:

Has anyone had any experience with them, and based on that what do you recommend?
(Also, does a radiant barrier impact your cell signals?
In our houses fans of any kind were largely ineffective. Radiant barrier made a huge difference on the other hand. There was no noticeable impact to phone signal.
Did you get it sprayed on?

Also, no impact on wifi within the house?
I used the roll kind, bought online from some place in DFW (atticbarrier.com?). It's stapled to the underside of the rafters, no need to tape edges.

Zero impact to wifi, or anything but the attic temperature. In San Antonio with a largely unshaded roof the attic would hang out around the mid-140s. After, high 90s. It performed best with continuous ridge and soffit venting.
Builder93
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AG
On a retrofit, a continuous ridge vent is the best thing along with adequate venting along the soffit. The idea is that you want a convective current in between each rafter so the heated air can escape everywhere. Also, the venting must be sized correctly so that you don't get a back draft.
ftworthag02
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AG
I looked into this several years ago for our 1915 home and found that solar fans are a waste and don't last long with our heat. Most research I found recommended soffit & ridge vents and more insulation.
6.5 Swede
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The Fife said:

Ferg said:

The Fife said:

Ferg said:

Has anyone had any experience with them, and based on that what do you recommend?
(Also, does a radiant barrier impact your cell signals?
In our houses fans of any kind were largely ineffective. Radiant barrier made a huge difference on the other hand. There was no noticeable impact to phone signal.
Did you get it sprayed on?

Also, no impact on wifi within the house?
I used the roll kind, bought online from some place in DFW (atticbarrier.com?). It's stapled to the underside of the rafters, no need to tape edges.


Zero impact to wifi, or anything but the attic temperature. In San Antonio with a largely unshaded roof the attic would hang out around the mid-140s. After, high 90s. It performed best with continuous ridge and soffit venting.
I also got the same results. I actually purchased the 2 rolls of the same kind although much cheaper from walmart. 6" overlap layer starting 12" from soffit to 12" from ridge vent creating an envelope / chimney effect.
6.5 Swede
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Builder93 said:

On a retrofit, a continuous ridge vent is the best thing along with adequate venting along the soffit. The idea is that you want a convective current in between each rafter so the heated air can escape everywhere. Also, the venting must be sized correctly so that you don't get a back draft.
This.
6.5 Swede
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Another thing to consider is that many homes have r-6 tubular duct work hung from the rafters. Moving this to the attic floor greatly reduces the surrounding air temp environment. Before I did that the bathroom nearest the ac discharge was 55 degs but the farthest room was 75 degs.
6.5 Swede
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Last thing I did was to replace my old 10 SEER 4 ton unit with a Goodman 19 SEER two stage 3/2 ton and variable speed air handler. I also bought an Goodman digital communication thermostat along with a remote sensor.

Most homes are controlled by a thermostat (even the stupid NEST) that closes contacts to turn on the compressor and blower which runs at a set speed. The Goodman communicates with the outside compressor allowing it to take control. It measures the outside air temp, condenser pressures, averages the thermostat and remote sensor, measures the indoor humidity, sets itself to either high 3 ton or low 2 ton mode depending on load and then controls the air handler speed for maximum efficiency. If the bedroom doors are closed or the filter is dirty it will additionally increase the speed. If all doors are open increasing return air flow it runs slower. It cools the home until the proper temp is met it then reduces the air speed thereby super chilling the evaporator coils to dehumidify the home. This has greatly reduced my cooling cost and increased our comfort. Previously my home would never would feel comfortable.

agracer
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AG
The Fife said:

Ferg said:

Has anyone had any experience with them, and based on that what do you recommend?
(Also, does a radiant barrier impact your cell signals?
In our houses fans of any kind were largely ineffective. Radiant barrier made a huge difference on the other hand. There was no noticeable impact to phone signal.
this. solar fans actually pull conditioned air out of your HOUSE which is the last thing you want.

Make sure your soffet vents are clear and put in some radiant barrier. I did this in my old house on Houston and the summer attic temps dropped 20+ degrees.

Also, make sure your ducts in the attic are hung properly and not tangled or leaking. Seal light openings and run a gasket around the attic stairs.

I used this and while it was a PITA to get in place, the drop in attic temp was worth the effort.

https://atticfoil.com/

There is a study by Texas A&M somewhere online that shows the attic foil pays for itself pretty quickly. The spray on stuff is also pretty worthless.
The Fife
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Yup, my payback came in less than a year by doing all that, I also bought an IR gun because heat cameras were (are still?) expensive.
evan_aggie
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AG
I've read quite the opposite regarding radiant barriers ( I should clarify: Radiant Boards w/ install cost ~$3000+) not being particularly cost effective. I suppose this changes if you add yourself with those foil sheets.

*shrug*

I ended up adding a powered thermostat controlled master flow fan. I set it to 105 and it hasn't kicked on yet. Last summer, we were doing a lot of work to our home, and I was in the attic often. It was brutal, and we had no passive vents high up: just gable slats/vents. Our home was built in 1949 and the roof boards run straight down to create an overhang w/o any place to add soffits.

I put a thermostat in the attic and monitored it getting upwards of 133-140F numerous times. I debated adding Whirlybird Turbines which is more fitting for a house our age, but the master flow was low profile and I liked the hood more to prevent unwanted rain intrusion when it blows sideways.

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