Energy Efficiency Ideas -- Attic

[nwdiver]

After doing some more research today, I learned that a metal duct may actually have an insulation layer on the inside. That could be what I have in my attic. I'll have to go up there again to check when I have some time. For now, I just wanted to provide an update that you may have to look extra close at a metal duct to tell if it's just a typical metal duct or one with insulation inside.

You have a built-in door blower test with your exhaust fan... it would be interesting to see before-after measurements if you do some air-sealing or cellulose blowing. If you can find an IR camera any leaks would be readily visible if it's hot outside and cool inside.

 

[Skotty]

You have a built-in door blower test with your exhaust fan... it would be interesting to see before-after measurements if you do some air-sealing or cellulose blowing. If you can find an IR camera any leaks would be readily visible if it's hot outside and cool inside.

Another question that popped into my head. I have fiberglass up there now. If I want to add extra insulation after air sealing, can I put cellulose on top of the fiberglass, or does the fiberglass need to be on top, or should they not be mixed and I should just use fiberglass since I already have fiberglass?

 

[nwdiver]

can I put cellulose on top of the fiberglass, or does the fiberglass need to be on top, or should they not be mixed and I should just use fiberglass since I already have fiberglass?

You can put cellulose right over whatever is there now...

Thought of a DIY manometer. Take a clear ~1" plastic tube. Stick one end outside near a window so you can see the level from inside. Fill it with water. Turn on your exhaust fan. Measure the level difference between outside and inside. After you add the insulation / Air Seal do it again and see if there's a difference....

 

[Skotty]

You can put cellulose right over whatever is there now...

Thought of a DIY manometer. Take a clear ~1" plastic tube. Stick one end outside near a window so you can see the level from inside. Fill it with water. Turn on your exhaust fan. Measure the level difference between outside and inside. After you add the insulation / Air Seal do it again and see if there's a difference....

Oh yeah. Kind of like a radon vacuum tube. I'll try that. The attic fan can move A LOT of air.

 

[Skotty]

Anyone know of any non-anecdotal statistics to give an idea of what the effectiveness range is for air sealing an attic? You would think some people somewhere who have had this done would actually provide real numbers for what the energy use difference was between years.

I found this. I guess it will do. Methodology for Estimated Energy Savings from Cost-Effective Air Sealing and Insulating | ENERGY STAR

 

[nwdiver]

Anyone know of any non-anecdotal statistics to give an idea of what the effectiveness range is for air sealing an attic? You would think some people somewhere who have had this done would actually provide real numbers for what the energy use difference was between years.

I found this. I guess it will do. Methodology for Estimated Energy Savings from Cost-Effective Air Sealing and Insulating | ENERGY STAR

I think there're too many variables. Air Sealing is going to be more important on cold winter days than hot summer ones... It's SUPER labor intensive to seal leaks manually. Your interior walls are hollow so all the tops provide a nice path too. Fire stops help but there's still some flow. My method of air sealing has alway been ~18"+ of cellulose.... larger gaps are easy to find. And you can look for dirty insulation as mentioned up thread...

If you can get a little negative pressure in the house air leaks are easy to spot with IR.

 

[Skotty]

Okay, yet another thing. I want to build a cover for the attic fan, since I only use at most for a couple of weeks in the fall and sometimes a week or two in the spring. But foam board insulation seems overpriced.

Example: Owens Corning FOAMULAR 150 1-1/2 in. x 4 ft. x 8 ft. R-7.5 Scored Squared Edge Insulation Sheathing-88WD - The Home Depot

It would probably take 4 sheets to build the cover. That's $100, and it's only R-7.5 foam board. The R-10 is over twice as expensive. Shouldn't this stuff be like $5 a sheet? Not $25? This isn't fancy electronics. It's a block of foam.

Here's something else that seems way overpriced: Tenmat Recessed Light Cover-FF130E - The Home Depot

 

[brkaus]

How about spray foam with ASTM E-84 Class 1 Approval? Does it mean anything?

 

[abasile]

Yes, foam board insulation is expensive! We spent several times what we would have for fiberglass or cellulose, but it was for a relatively small space so the cost of the materials was not that big a deal.

 

[Alketi]

Anyone know of any non-anecdotal statistics to give an idea of what the effectiveness range is for air sealing an attic? You would think some people somewhere who have had this done would actually provide real numbers for what the energy use difference was between years.

I found this. I guess it will do. Methodology for Estimated Energy Savings from Cost-Effective Air Sealing and Insulating | ENERGY STAR

Skotty, I don't have numbers, but it's as intuitive as it sounds -- the house blows air out the top, and any unadulterated pathway in the attic will pull conditioned air out in the winter.

Heat goes from more to less. So in the summer, these open pathways will also bring hot air into your living space.

More from my attic.

A poorly sealed double-wall in the bathroom as viewed from the attic (see all the dirty insulation?):

Sealed with 2" foam board and Great Stuff:

Covered with cellulose:

 

[Skotty]

Okay, yet another thing. I want to build a cover for the attic fan, since I only use at most for a couple of weeks in the fall and sometimes a week or two in the spring. But foam board insulation seems overpriced.

Example: Owens Corning FOAMULAR 150 1-1/2 in. x 4 ft. x 8 ft. R-7.5 Scored Squared Edge Insulation Sheathing-88WD - The Home Depot

It would probably take 4 sheets to build the cover. That's $100, and it's only R-7.5 foam board. The R-10 is over twice as expensive. Shouldn't this stuff be like $5 a sheet? Not $25? This isn't fancy electronics. It's a block of foam.

Here's something else that seems way overpriced: Tenmat Recessed Light Cover-FF130E - The Home Depot

It occurred to me last night that I don't have to build the side walls of the attic fan cover out of expensive foam board. I can just use wood on the sides and ensure it's sealed, as there will be attic insulation surrounding it. So I only need the expensive foam board for the top cover.

 

[Ulmo]

After doing some more research today, I learned that a metal duct may actually have an insulation layer on the inside. That could be what I have in my attic. I'll have to go up there again to check when I have some time. For now, I just wanted to provide an update that you may have to look extra close at a metal duct to tell if it's just a typical metal duct or one with insulation inside.

All non-school-season summer at a school we replaced ducts that had insulation inside with ducts that have insulation outside (then another layer of plastic outside that) at an elementary school. They reused a few of the inside-insulated ducts, but mostly they were replaced. I have to wonder if they think that's some sort of health hazard to have insulation inside the plenum.

 

[Ulmo]

You have a built-in door blower test with your exhaust fan... it would be interesting to see before-after measurements if you do some air-sealing or cellulose blowing. If you can find an IR camera any leaks would be readily visible if it's hot outside and cool inside.

Is that a diffuser fan or a directional fan? (They should both work for the FLIR test, but just one quick note, that diffuser fans like to cause helpful turbulence in the vicinity of the fan targets, whereas directional fans cause more directional flow (and less intentional turbulence); the diffuser fan should do some air movement overall, and would work with that test, but the directional ones are much better at air movement from place to another place; just know the difference between those so you don't get baffled or surprised by the results.)

 

[Skotty]

Is that a diffuser fan or a directional fan? (They should both work for the FLIR test, but just one quick note, that diffuser fans like to cause helpful turbulence in the vicinity of the fan targets, whereas directional fans cause more directional flow (and less intentional turbulence); the diffuser fan should do some air movement overall, and would work with that test, but the directional ones are much better at air movement from place to another place; just know the difference between those so you don't get baffled or surprised by the results.)

Well, it pushes A LOT of air. If you open only one window and turn on the fan, you can go back to that window and the air will be blowing through hard. Can blow stuff off desks.

I haven't checked the ducts yet to see if they have insulation inside. Maybe they do, maybe they don't. I have to get some supplies before I can find out, as I have to take one of the runs apart in order to find out. Doesn't seem very big though, so if it does have insulation, it's not much, or it's a very small run for all the rooms it services.

 

[nwdiver]

I haven't checked the ducts yet to see if they have insulation inside. Maybe they do, maybe they don't. I have to get some supplies before I can find out, as I have to take one of the runs apart in order to find out. Doesn't seem very big though, so if it does have insulation, it's not much, or it's a very small run for all the rooms it services.

Depending on how old your AC is, how much you spend on cooling/heating and how much you're willing to invest... #2 on my list of cost effective improvements is replacing a central air with a ductless system. You can still use the central air system for circulation but a multi-split can often reduce energy use by >50% with proper zoning. I spent $3k on a 2 ton 3 zone system and it dropped my energy consumption by ~500kWh/mo.

 

[Skotty]

Depending on how old your AC is, how much you spend on cooling/heating and how much you're willing to invest... #2 on my list of cost effective improvements is replacing a central air with a ductless system. You can still use the central air system for circulation but a multi-split can often reduce energy use by >50% with proper zoning. I spent $3k on a 2 ton 3 zone system and it dropped my energy consumption by ~500kWh/mo.

A/C unit is an American Standard Allegiance 14, SEER 14. Heat is some sort of Lennox gas unit, though didn't see an actual model number on it anywhere. Has sticker on it saying it was converted to a Honeywell ignition control.

I'd have a hard time switching to a "ductless" system. Gives me horrifying flashbacks of living in an old trailer home with a window unit.

 

[nwdiver]

I'd have a hard time switching to a "ductless" system. Gives me horrifying flashbacks of living in an old trailer home with a window unit.

The new ones are indistinguishable from central air if you get a ceiling cassette.