What’s your Attic Temp? (Trying to decide on going from R19 to R49)

launboy · 01-24-21, 11:31 AM

Winter here in Wisconsin and my attic temp is measuring 15*F above outdoor temp on average with no snow on the roof, and now with some snow last night I’m seeing 20*F above outdoor.

I’ve got R19 fiberglass batt parallel with trusses now. Trying to decide if I’ll see the payback on bringing it up to the code R49 for my area.

15-20* above outdoor means my attic is above freezing which means melting and ice dams in gutters. If adding insulation brings attic temp below freezing it’s a win win energy savings and no ice.

Anyone else measure attic temp or have experience with this sort of improvement?

JRMichler · 01-28-21, 03:03 PM

I'm up in Northern Wisconsin, and have some experience with this.

My shop is heated to 65 degrees, has the ceiling insulated to R80 with the soffit vents plugged. That roof never has ice dams, even with three feet of snow on it.

My house has R96 (!) insulation in the ceiling, and is heated to 72 degrees. Again, never any ice dams.

The gas bill for the house, domestic hot water, and shop has only once exceeded $100.00 in the last seven years.

nibs · 02-26-21, 05:05 PM

IMO insulation is like fun and money, you can never have too much. The lid in my house is R70, we have no attic, but the snow does not melt unless the ambient temp is above freezing.

WillyP · 02-26-21, 05:49 PM

I worked my way through college as an insulator. So I am a little Biased. But it is well worth the money to invest in insulating up to the local requirements. This is especially true if you plan on keeping your house for more than three years. Some of the big box stores rent out the equipment to blow cellulose in yourself. Where I live they will lend it to you for free if you buy a certain number of bags of insulation.
Batts have a reputation for leaks, because there is almost always spaces between the batt and the joist. SO even if you have R19 batts, there are probably places where you have no insulation or only an R10 (or less). Blowing something like cellulose over top of the batts will improve the insulation system, more than the numbers might reflect.

GaryGary · 02-26-21, 08:13 PM

Hi,

Here are some temperatures logged in my attic for quite a few months for whatever its worth:

https://www.builditsolar.com/Experim...AtticTemps.htm

Note the large daily swings -- I wonder if you are weighing the daytime period with solar heating too much? Nights are long in the winter.
I'm located in SW Montana.

You can blow in cellulose with a blower that Home Depot will loan you for nothing as long as you buy the insulation there -- cost is very low.

Gary

jeff5may · 02-27-21, 11:17 PM

I moved into a fairly new house about 2 years ago. I was having sticker shock the first winter. That month, I went to the big box store and blew up 8 inches of cellulose into the top floor attic. The kids, living in upstairs bedrooms, immediately noticed the difference. I made my money back that winter on the insulation.

I Also noticed that the heat pump was defrosting every couple hours, whether or not the outdoor unit was frosty. Pulled the panel and figured out the coil sensor wasn't connected correctly. Flashy light codes and such.

Between the insulation and the heat pump troubleshooting, my heating bill chopped in half by the time it really got cold.

This is in a stick built home, somewhat cape cod style. Same basic layout as the left side of Gary's example house. 2 story with a below grade basement. 14 seer trane 2.5 ton heat pump covers the whole year. Upstairs bathroom is in a dormer, and the plumbing just froze last week during single digit weather. No complaints about comfy bedrooms from kids, only that the water won't run. Thank God for pex pipe.

jeff5may · 02-27-21, 11:55 PM

Being the winter, now is the best time to get an infrared camera and hunt down the heat leaks. There was nowhere to rent one where I live, so I ended up buying a seek. Flir makes one now that is about the same price. At the time, flir only had one for the iPhone and I had Android. Didn't want to go all out on a super pro model, just something I could hook up to my phone.

The seek camera was the best envelope improvement tool I used on the house. I'm sure the expensive models do an even better job. I mean, I've done insulation in ceilings and hunted down drafts and such before, but that little camera justified the insulation in the top floor attic in about 5 minutes. The ground floor attic in the house is behind the upstairs bedroom walls and it was obvious that most of the heat leaking from the house was from the top attic. I will eventually get around to blowing cellulose into those areas, but that first winter I didn't. The camera showed me where the heat was passing through, and I just taped up a few batts and evened them out where they needed it.

After I was done with the project, I sold the seek camera on FB market for around 20 bucks less than I paid for it.

01-24-21, 11:31 AM	#1
launboy Apprentice EcoRenovator Join Date: Mar 2011 Location: SE Wisconin Posts: 107 Thanks: 3 Thanked 11 Times in 9 Posts	What’s your Attic Temp? (Trying to decide on going from R19 to R49) Winter here in Wisconsin and my attic temp is measuring 15F above outdoor temp on average with no snow on the roof, and now with some snow last night I’m seeing 20F above outdoor. I’ve got R19 fiberglass batt parallel with trusses now. Trying to decide if I’ll see the payback on bringing it up to the code R49 for my area. 15-20* above outdoor means my attic is above freezing which means melting and ice dams in gutters. If adding insulation brings attic temp below freezing it’s a win win energy savings and no ice. Anyone else measure attic temp or have experience with this sort of improvement? Last edited by MetroMPG; 02-26-21 at 07:36 AM.. Reason: (added info to title)

02-27-21, 11:17 PM	#6
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,431 Thanks: 431 Thanked 619 Times in 517 Posts	I moved into a fairly new house about 2 years ago. I was having sticker shock the first winter. That month, I went to the big box store and blew up 8 inches of cellulose into the top floor attic. The kids, living in upstairs bedrooms, immediately noticed the difference. I made my money back that winter on the insulation. I Also noticed that the heat pump was defrosting every couple hours, whether or not the outdoor unit was frosty. Pulled the panel and figured out the coil sensor wasn't connected correctly. Flashy light codes and such. Between the insulation and the heat pump troubleshooting, my heating bill chopped in half by the time it really got cold. This is in a stick built home, somewhat cape cod style. Same basic layout as the left side of Gary's example house. 2 story with a below grade basement. 14 seer trane 2.5 ton heat pump covers the whole year. Upstairs bathroom is in a dormer, and the plumbing just froze last week during single digit weather. No complaints about comfy bedrooms from kids, only that the water won't run. Thank God for pex pipe. Last edited by jeff5may; 02-28-21 at 12:03 AM..

01-28-21, 03:03 PM	#2
JRMichler Apprentice EcoRenovator Join Date: Apr 2012 Location: Phillips, WI Posts: 109 Thanks: 10 Thanked 30 Times in 25 Posts	I'm up in Northern Wisconsin, and have some experience with this. My shop is heated to 65 degrees, has the ceiling insulated to R80 with the soffit vents plugged. That roof never has ice dams, even with three feet of snow on it. My house has R96 (!) insulation in the ceiling, and is heated to 72 degrees. Again, never any ice dams. The gas bill for the house, domestic hot water, and shop has only once exceeded $100.00 in the last seven years.

02-26-21, 05:05 PM	#3
nibs Apprentice EcoRenovator Join Date: Jun 2010 Posts: 206 Thanks: 1 Thanked 18 Times in 17 Posts	IMO insulation is like fun and money, you can never have too much. The lid in my house is R70, we have no attic, but the snow does not melt unless the ambient temp is above freezing.

02-26-21, 05:49 PM	#4
WillyP Helper EcoRenovator Join Date: Jul 2020 Location: Virginia Posts: 30 Thanks: 8 Thanked 3 Times in 3 Posts	I worked my way through college as an insulator. So I am a little Biased. But it is well worth the money to invest in insulating up to the local requirements. This is especially true if you plan on keeping your house for more than three years. Some of the big box stores rent out the equipment to blow cellulose in yourself. Where I live they will lend it to you for free if you buy a certain number of bags of insulation. Batts have a reputation for leaks, because there is almost always spaces between the batt and the joist. SO even if you have R19 batts, there are probably places where you have no insulation or only an R10 (or less). Blowing something like cellulose over top of the batts will improve the insulation system, more than the numbers might reflect.

02-26-21, 08:13 PM	#5
GaryGary Apprentice EcoRenovator Join Date: Nov 2008 Location: SW Montana Posts: 139 Thanks: 1 Thanked 21 Times in 15 Posts	Hi, Here are some temperatures logged in my attic for quite a few months for whatever its worth: https://www.builditsolar.com/Experim...AtticTemps.htm Note the large daily swings -- I wonder if you are weighing the daytime period with solar heating too much? Nights are long in the winter. I'm located in SW Montana. You can blow in cellulose with a blower that Home Depot will loan you for nothing as long as you buy the insulation there -- cost is very low. Gary

02-27-21, 11:55 PM	#7
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,431 Thanks: 431 Thanked 619 Times in 517 Posts	Being the winter, now is the best time to get an infrared camera and hunt down the heat leaks. There was nowhere to rent one where I live, so I ended up buying a seek. Flir makes one now that is about the same price. At the time, flir only had one for the iPhone and I had Android. Didn't want to go all out on a super pro model, just something I could hook up to my phone. The seek camera was the best envelope improvement tool I used on the house. I'm sure the expensive models do an even better job. I mean, I've done insulation in ceilings and hunted down drafts and such before, but that little camera justified the insulation in the top floor attic in about 5 minutes. The ground floor attic in the house is behind the upstairs bedroom walls and it was obvious that most of the heat leaking from the house was from the top attic. I will eventually get around to blowing cellulose into those areas, but that first winter I didn't. The camera showed me where the heat was passing through, and I just taped up a few batts and evened them out where they needed it. After I was done with the project, I sold the seek camera on FB market for around 20 bucks less than I paid for it.