Energy Efficiency Ideas -- Attic

[Skotty]

Anyone care to comment on the ideas presented here?

The Most Cost Effective Efficient Attic Solution

Not on their endorsed products necessarily, but just the ideas presented.

I'm thinking of doing some of the things presented on this site.

Here's a quick summary of everything they discuss:
1) Installing radiant barrier on roof rafters
2) Ensure good attic ventilation; they mention possibly using solar attic fan
3) Air sealing the ceiling -- 1 inch coat of spray foam beneath other insulation
4) Air sealing the ceiling -- Recessed light covers (recommends only using efficient bulbs so as not to overheat fixtures)
5) Air sealing the ceiling -- Attic stair cover
6) Air seal and insulate any duct work in attic

 

[Skotty]

Note that my attic gets ridiculously hot in the summer.

 

[Uncle Paul]

Looking at a Quiet Cool whole house fan installed into the attic.

Turn it on when the outside air is cooler than the inside.

It sucks fresh, cooler air into an open window or door, and blows the hotter air in the house out through the attic vents, also taking the even hotter air with it.

Quieter than older attic fans as it is hung from rafters with straps, rather than being bolted into the framing.

Neighbor has one and he says he runs his AC 1/2 as much as before installation.

 

[bkp_duke]

If you install radiant barrier, please install lightning rods on your house. When we lived in TX a neighbor had lightning strike their house and run through the radiant barrier. I did not know it at the time, but the insurance considered it a fire risk in lightning-prone areas.

 

[DrivingRockies]

Looking at a Quiet Cool whole house fan installed into the attic.

I love mine. (Probably a different brand though)

For those that don't know, a whole house fan is quite different than an attic fan. Both can be useful in their own right. I decided against that attic fan as I was getting the whole house fan.

 

[nwdiver]

Anyone care to comment on the ideas presented here?

The Most Cost Effective Efficient Attic Solution

Not on their endorsed products necessarily, but just the ideas presented.

I'm thinking of doing some of the things presented on this site.

Here's a quick summary of everything they discuss:
1) Installing radiant barrier on roof rafters
2) Ensure good attic ventilation; they mention possibly using solar attic fan
3) Air sealing the ceiling -- 1 inch coat of spray foam beneath other insulation
4) Air sealing the ceiling -- Recessed light covers (recommends only using efficient bulbs so as not to overheat fixtures)
5) Air sealing the ceiling -- Attic stair cover
6) Air seal and insulate any duct work in attic

IMO adding blown cellulose is BY FAR the best home improvement you can do. BY FAR.

I'm not sold that air sealing is worth the trouble if you blow cellulose. Can't imagine that anything is more cost effective than ~16" of blown cellulose insulation. It's relatively cheap, easy to install, and it's made of recycled newspaper. Once the cellulose settles is pretty air-tight... at least as much as you would want in a house.

 

[Xenoilphobe]

I did 5 inches of open cell foam in my attic. They sprayed the Attic Ceiling (area under the asphalt shingles and sprayed the ridge vent and soffits closed and its now conditioned space. Temps in the summer are 70 degrees and our utility bills dropped about 30% (got new doors and windows at the same time) so I would say the percentage would be hard to independently calculate.

The best is we dont hear wind, rain or airplanes anymore!!!! We have two HVAC systems and one died this summer - we didn't know for weeks because the upstairs unit carried the 6000 SF load!!!! When the tech came out to repair the basement system he couldn't believe the attic when he saw it, on a 102 degree day - he didn't want to go in the attic - so I told him I would go with him - he was shocked when we went upstairs - he told me that this should be code for new builds - he also said it solves many problems (stops radiant heat transfer, all ductwork is now inside the conditioned envelope and the HVAC system is also inside the conditioned space and performs much more efficiently. He told me when the system goes - we should just get a split system and go from 2 - 2 ton systems to a single 2 ton system...

Also - in high wind our house used to creak - I had them spray 3 inches of closed cell foam on the End Gables to re-enforce this area and the creaking has stopped. We also had our garage completely spray foamed with open cell foam as well, used close cell on the gables - as this area showed the most air leakage into the house (we used a FLIR gun to check everything)

We also close cell foamed the foundation in the basement - the FLIR gun showed that we had significant leakage here and now doesn't even register any temperature change with 5 inches of close cell foam sprayed in this area.

If I ever build new - I am doing the whole house with the same product - http://www.sealection500.com/Repository/Image/sealection-agribalance-flyer.pdf

Also I use NEST thermostats - according to their statics our house is rated in the top 5% of efficient homes in our area based on HVAC run time only. This rating is achieved with us using a 2007 13 SEER system and 70 AFUE heat system. (not sure how they calculate this, but I had to input data on house size, orientation, age, HVAC system data etc).

If I upgraded to a smaller HVAC with a AFUE of 97% and 22 SEER I bet we could be in the top 1%... and my wallet would be $8000 lighter too..

 

[SageBrush]

If the primary intent is to solve hot attic space...
An attic fan is cheap and easy. I would start there and see how close to ambient the attic reaches.

Winter is a different story and depends on how much attic space you are willing to sacrifice. Certainly insulation between the rafters followed by say drywall and tightening up the space against air leaks seems reasonable.

I personally would not do anything to the ceiling from below because I dislike squat spaces.

 

[nwdiver]

If the primary intent is to solve hot attic space...

Unless there's a specific reason to keep the attic cool there's really nothing wrong with a hot attic provided the ceiling is well insulated. A ridge vent is probably far more effective than an attic fan. I was a huge proponent of radiant barriers until I ran the numbers of having a radiant barrier under the roof and ~18" of cellulose insulation on the ceiling. The benefit is negligible.

 

[SageBrush]

A ridge vent is probably far more effective than an attic fan.

What is a ridge vent and why is it more effective than a fan ?

Addendum: are you talking about an opening at the apex of a roof ? I presume heat escapes via a chimney effect but I don't understand why it is more effective than a fan. I have now learned that an attic fan is probably best not mixed with a ridge vent already in place.

 

[nwdiver]

What is a ridge vent and why is it more effective than a fan ?

Addendum: are you talking about an opening at the apex of a roof ? I presume heat escapes via a chimney effect but I don't understand why it is more effective than a fan.

Yes. Passive chimney effect.

The majority of roofing experts agree that ridge vents are the most effective and cost-effective roof vents available.

 

[Xenoilphobe]

more detail

 

[Skotty]

Unless there's a specific reason to keep the attic cool there's really nothing wrong with a hot attic provided the ceiling is well insulated. A ridge vent is probably far more effective than an attic fan. I was a huge proponent of radiant barriers until I ran the numbers of having a radiant barrier under the roof and ~18" of cellulose insulation on the ceiling. The benefit is negligible.

Is it worthwhile to keep rooftop solar wiring and combiner boxes cooler? Right now, the plan is to run all the rooftop solar wiring through the attic.

Also, my 2nd floor duct work runs through the attic. It uses insulated tubes, but might still be a factor.

Another reason to keep it cooler is because it just stupid hot if you go up there in the summer, and would be nice if it were cooler. Reasons I might go into attic: to measure stuff, to install lighting, to run network or other cabling, to check for wasps or other bug issues.

I just installed a remote temp sensor in the attic. Going to take regular measurements of attic temp vs outdoor temp. I just love statistics, charts, and graphs.

I kind of like the idea of a solar powered attic vent fan for the summer (When do you need the most ventilation? On a sunny summer day!) But would it be counterproductive in the winter? If so, maybe install a switch, and switch it off in the winter.

 

[outie]

I did 5 inches of open cell foam in my attic. They sprayed the Attic Ceiling (area under the asphalt shingles and sprayed the ridge vent and soffits closed and its now conditioned space. Temps in the summer are 70 degrees and our utility bills dropped about 30% (got new doors and windows at the same time) so I would say the percentage would be hard to independently calculate.

The best is we dont hear wind, rain or airplanes anymore!!!! We have two HVAC systems and one died this summer - we didn't know for weeks because the upstairs unit carried the 6000 SF load!!!! When the tech came out to repair the basement system he couldn't believe the attic when he saw it, on a 102 degree day - he didn't want to go in the attic - so I told him I would go with him - he was shocked when we went upstairs - he told me that this should be code for new builds - he also said it solves many problems (stops radiant heat transfer, all ductwork is now inside the conditioned envelope and the HVAC system is also inside the conditioned space and performs much more efficiently. He told me when the system goes - we should just get a split system and go from 2 - 2 ton systems to a single 2 ton system...

Also - in high wind our house used to creak - I had them spray 3 inches of closed cell foam on the End Gables to re-enforce this area and the creaking has stopped. We also had our garage completely spray foamed with open cell foam as well, used close cell on the gables - as this area showed the most air leakage into the house (we used a FLIR gun to check everything)

We also close cell foamed the foundation in the basement - the FLIR gun showed that we had significant leakage here and now doesn't even register any temperature change with 5 inches of close cell foam sprayed in this area.

If I ever build new - I am doing the whole house with the same product - http://www.sealection500.com/Repository/Image/sealection-agribalance-flyer.pdf

Also I use NEST thermostats - according to their statics our house is rated in the top 5% of efficient homes in our area based on HVAC run time only. This rating is achieved with us using a 2007 13 SEER system and 70 AFUE heat system. (not sure how they calculate this, but I had to input data on house size, orientation, age, HVAC system data etc).

If I upgraded to a smaller HVAC with a AFUE of 97% and 22 SEER I bet we could be in the top 1%... and my wallet would be $8000 lighter too..

My house currently has no insulation at all (very old house). While we live on coastal area the temperature fluctuates a lot during the hottest / coldest days. I have been thinking about insulation but not sure which to go with. As mentioned the house does not have insulation whatsoever so will the attic insulation help much? The walls are still not insulated.

I also like to run/add my own network cables every once in a while, will the blown insulation be applied at the attic floor? If yes that will interfere if I decided to run more cables. If it's only applied below the roof then doesn't that also seal in the heat trapped inside the attic?

 

[abasile]

We have an attic-type space with 2x12 roof joists that are 12" on center. Our contractor bought a bunch of high-quality foam board insulation (1.5" and 1" thick boards) and cut it into strips to pack it in layers between the joists, where it completely fills the empty space. Below the joists, he installed drywall. This attic/room is now the best insulated space in our home, and it stays very comfortable year round. One great thing about hard foam directly against the roof deck is that it seems to eliminate the risk of condensation arising from warm, moist air coming in contact with a cold roof deck (and potentially getting absorbed by fiberglass or cellulose insulation).

 

[Xenoilphobe]

My house currently has no insulation at all (very old house). While we live on coastal area the temperature fluctuates a lot during the hottest / coldest days. I have been thinking about insulation but not sure which to go with. As mentioned the house does not have insulation whatsoever so will the attic insulation help much? The walls are still not insulated.

I also like to run/add my own network cables every once in a while, will the blown insulation be applied at the attic floor? If yes that will interfere if I decided to run more cables. If it's only applied below the roof then doesn't that also seal in the heat trapped inside the attic?

It will definitely help with with temperature control. The biggest heat generation area of a home is the exposed roof (I noticed a big change in temps when I added Solar Panels) - just because the roof was shaded on the southern exposure.

Do you have window AC units or a HVAC system? You need to "condition" the space below - the heat is actually radiating down - and the heat radiating up is actually at a much lower temperature - if you are conditioning the space below. I am not an insulation, guy - so you should talk to one that specializes in older structures and foam - keep in mind you can get a "whole envelope" tax credit - you should ask them about that.

In my home the attic floor is completely clear (in my case they removed all the old fiberglass batts and the blown in cellulose insulation. I can now easily work up there with passing out from the heat and I have been able to add lighting to the closets and run ethernet to each of the kids rooms for gaming and video streaming to their TV's. I have also added attic lighting and a couple of outlets up there for Access Points and a Cell Repeater. I am even thinking about moving a small computer rack up there now, but I think the cooler temps in the basement are better for the media server and security camera servers. I mounted a half rack touching the ceiling in the basement so that if we have water leakage it doesn't damage the equipment.

Also you want to use open cell foam in the attic so that moisture is allowed to radiate out of the structure and this will reduce the ability for mold to grow in a coastal home. Additionally if your roof leaks - it will drip through open cell foam and you will know where the leak is - if you use close cell - and the roof leaks - it will rot the whole section out - and you won't be able to detect it until it is already damaged.

If you decide to spray foam the walls I would recommend closed cell in the foundation up to the "water line" of any potential flood plain. The great thing about closed cell is can be submerged in water and not be damaged - so it great to use in areas were you have the potential for flooding. The closed cell will transmit more sound, but you can add a 1 inch layer of open cell and this will stop the sound intrusion. Also Closed cell will add a massive amount of structural integrity to your home and help in high wind events..

If I lived in coastal Texas and had to rebuild - I would rebuild with Spray Foam verses cellulose or fiberglass batts.

I would see if you can get someone out to check out your options. AM Construction Insulates Coastal Home on Seal Beach with Open-Cell and Closed-Cell Spray Foam | Spray Foam Contractors | Spray Foam News - SprayFoam.com I dont know these guys, but might be worth a call.

 

[nwdiver]

Is it worthwhile to keep rooftop solar wiring and combiner boxes cooler? Right now, the plan is to run all the rooftop solar wiring through the attic.

Also, my 2nd floor duct work runs through the attic. It uses insulated tubes, but might still be a factor.

Another reason to keep it cooler is because it just stupid hot if you go up there in the summer, and would be nice if it were cooler. Reasons I might go into attic: to measure stuff, to install lighting, to run network or other cabling, to check for wasps or other bug issues.

I just installed a remote temp sensor in the attic. Going to take regular measurements of attic temp vs outdoor temp. I just love statistics, charts, and graphs.

I kind of like the idea of a solar powered attic vent fan for the summer (When do you need the most ventilation? On a sunny summer day!) But would it be counterproductive in the winter? If so, maybe install a switch, and switch it off in the winter.

A lot of that comes down to cost effectiveness...

Insulating the roof with spray foam works great to keep your attic 'cool' ~85F. I lived in a house in TX with a spray foam insulated roof. Working in the attic wasn't too back. But when I installed solar it was a PITA. It's impossible to check to see that the bolts for the feet were in a rafter and you can't check for leaks. You're also increasing the air conditioned space of the home by ~20% since the roof is now the boundary instead of the ceiling. In the evenings after it cooled off outside we'd open the windows... heat would radiate into the house from the attic for hours.... So for the added cost you're using more energy for air conditioning.

I don't think the temperatures you see in an attic would harm wiring. The wiring should be designed for 90C. That's 194F... if your attic is getting that hot you have other issues... I don't think radiant barrier is worth the cost if your ceiling is properly insulated (and if it's not then insult the ceiling). But... if you want to keep your attic cool for when you're working up there I think a radiant barrier attached across the rafters combined with ridge & soffet vents would probably be more effective than active ventilation.

I measured the air temperature in that gap between the radiant barrier and the roof once... IIRC it was ~140F. All that hot air gets rejected from the ridge vent and cooler air is drawn in from the soffits so you get very efficient convection flow removing the warmest air from the attic.

With proper insulation the heat transferred to the house from the attic is virtually identical with or without the radiant barrier. So the most cost effective solution to what this diagram is showing is to add more insulation to the ceiling NOT a radiant barrier.... unless your goal is a cooler attic and not a smaller electric bill....

 

[SageBrush]

You're also increasing the air conditioned space of the home by ~20% since the roof is now the boundary instead of the ceiling.

Is that a given ? I understand that air will not flow up, but it could still flow sideways through vents if the goal is ambient. My implied bias is to avoid heat transfer from the hot asphalt shingles.

if you want to keep your attic cool for when you're working up there I think a radiant barrier attached across the rafters combined with ridge & soffet vents would probably be more effective than active ventilation.

I take it that the radiant barrier does not cover the apex of the attic where the ridge is placed ? What fraction of the attic heat is from radiation alone ?

Sorry for the dumb questions. I am not well informed but would like to be!

 

[Xenoilphobe]

I paid about $4K to do my attic and two car garage - I am stunned that laws haven't been passed to mandate foam due to its superior insulation factors. I suspect the fiberglass batt lobby combined with cheap builders who just want to slam up a structure and sell it have limited the growth of SF to a higher end, more educated consumer market.

You can also buy spray foam as a consumer, but I was only able to find closed cell - this is what I used to seal up my soffits and around the foundation. cures in about an hour.

HANDI-FOAM P10726 Spray Foam Kit II-205 Class 1, 41 lb
Average ratingut of5stars, based onreviewsWrite a reviewratings
By: Handi-Foam

Read more....

 

[SmartElectric]

My local hardware store included a blower rental with purchase of a pallet of cellulose insulation. Did the DIY blown cellulose job with my wife almost 10 years ago. I made a "slight" miscalculation, meant to add 2' of insulation, but ended up with 4' .. oops, a little more doesn't hurt. Dropped out heating/cooling bills dramatically. Total cost $300.

Canada had a national home efficiency program, they suck air out of the house with a large fan to measure the air loss. We had 8' x 8' effective air loss envelope. During this process, we went around the top floor and found all of the places air was coming into the walls and ceiling. Spray foamed each of these spots. Dropped the air movement down to 3' x 2' air loss envelope. We stopped then, don't want "air tight", you need movement for health of the house and you.
Total cost $200. Made a dramatic different to comfort during cold days.

This is in a 1940's wood cape cod dormer house, if we can make this old gal livable, you can too.