Attic Insulation

[Nelson]

Looking for some opinions/experiences with replacing/upgrading attic insulation...

A little background for some context.

We moved into the house last June. The home was built in the mid-70s. Initial inspection of the home didn't raise any concerns about the attic insulation. Comment was that the insulation was acceptable (somewhere in the R20 range). This winter, we had some fairly large ice damming. We use propane for heating (suplementing with wood) and we were burning through it more quickly than I had anticipated. We also have ~40 canned lights throughout the house. This lead me down the path of researching attics, insulation, air sealing, etc, etc.. Bottom line is that we need to address the attic by properly air sealing it and upgrading the insulation.

I've had several contractors out to get an idea on pricing for air sealing the attic and adding/replacing the insulation and getting it up to R50. We have ~6 in of chopped fiberglass up there now. On contractor stated that in order to properly air seal the attic, it would be best to completely remove all the existing insulation, air seal and then blow in new insulation. The other contractor stated that we wouldn't HAVE to remove the old insulation and that he could work around it to do the air sealing. Then blow in insulation on top of existing. The difference in price between completely removing the insulation and leaving it there is about $2000.

Soooooo, here's where I'm looking for opinions and experience. Should we completely remove the old insulation or am I just wasting $2K by doing that? My concern would be around how good of an air sealing job they could by just pushing the old insulation aside. My gut tells me to bite the bullet and start with from scratch by removing the old insulation, properly air sealing and blowing in new insulation.

TIA

 

[midwestcoast]

it's really gonna come down to how match attention to detail the contractor that you pick provides.
it may be easier to air seal with all the old insulation gone but that doesn't matter if the workers don't do it properly. On the other hand the guys who leave the old FG in place could conscientiously move it aside, air-seal & them move it back, or they could just use it as an excuse to do a crappy job of air-sealing.

 

[woodgeek]

I had the same decision to make last year, and opted to leave the old stuff. If it was full of mouse droppings or mold, I might consider pulling it, otherwise not. The $2k is just profit for that contractor who invested in a truck mounted vacuum to do that work IMO, and in service of customer OCD. Insulation is insulation, and the FG is not hard to push around during the airsealing work (I did 90% of my attic airsealing DIY).

With 40 can lights into your attic, and WI snow, I am not surprised you have ice dams!! Those suckers will be a bear. I had 6 of those (installed 6 mos before I moved in, on realtor advice to the previous owner) and I still flinch when I look at them. I ended up pulling out 2 and restoring the drywall and drop light fixture in one location. Unless they are airtight insulation contact units, the contractor will have to build an airtight enclosure over each one, using a big cardboardy flower-pot dohickey, Tanmat is one maker. PITA times 40. I've got 4 of them.

I went with cellulose blown over to R-50 total. No regrets. In your climate, I might go a little deeper.

The airsealing will be the best thing you ever did to that house, and you will not regret it. You will be a lot more comfortable and save a bundle. My only regret is that I didn't have pros do it year 1, instead of doing it myself in dribs and drabs for a few years, and then have them finish the stuff I couldn't reach.

 

[EatenByLimestone]

RE: removing the old insulation...

What are they removing?

Is there a space concern here?

What are they replacing it with?

The reason I ask, is if they are removing something that is R-3 and replacing it with R-6 in a spot that doesn't have a lot of space to blow new stuff in you could be short changing yourself if you don't have the old stuff taken out. If there aren't any space concerns and the guy sealing from below or moving stuff aside is careful, adding it to the top isn't going to hurt anything.

 

[Nelson]

I had the same decision to make last year, and opted to leave the old stuff. If it was full of mouse droppings or mold, I might consider pulling it, otherwise not. The $2k is just profit for that contractor who invested in a truck mounted vacuum to do that work IMO, and in service of customer OCD. Insulation is insulation, and the FG is not hard to push around during the airsealing work (I did 90% of my attic airsealing DIY).

With 40 can lights into your attic, and WI snow, I am not surprised you have ice dams!! Those suckers will be a bear. I had 6 of those (installed 6 mos before I moved in, on realtor advice to the previous owner) and I still flinch when I look at them. I ended up pulling out 2 and restoring the drywall and drop light fixture in one location. Unless they are airtight insulation contact units, the contractor will have to build an airtight enclosure over each one, using a big cardboardy flower-pot dohickey, Tanmat is one maker. PITA times 40. I've got 4 of them.

I went with cellulose blown over to R-50 total. No regrets. In your climate, I might go a little deeper.

The airsealing will be the best thing you ever did to that house, and you will not regret it. You will be a lot more comfortable and save a bundle. My only regret is that I didn't have pros do it year 1, instead of doing it myself in dribs and drabs for a few years, and then have them finish the stuff I couldn't reach.

Thanks for the reply Woodgeeok. We love the canned lights from an inside of the house perspectice but, yeah, might as well just punch a hole in the drywall from a building envelope perspective! I've replaced 3 of them with LED retrofit unit. Infrared showed pretty much zero air loss with these units which is great. Though, they run about $25-$30 per. I've already put regular LED lights in ~10 of the cans so I will likely just have them cap and foam a majority of the cans.

Definitely looking forward to what effect the air sealing has. We are first time propane users and for the first time in our home owning lives, we had to set the thermo to 66 throughout the winter. Would much rather be in the 68-70 range. Working on my stove situation in addition to this.

I did think about doing the air sealing myself. However, I took one look up in the attic and that was that. Low sloped roof, 2100 sq ft, and dark as mud. No way I'm going up there. I can do a lot of things myself but this isn't going to be one of them!

 

[Nelson]

RE: removing the old insulation...

What are they removing?

Is there a space concern here?

What are they replacing it with?

The reason I ask, is if they are removing something that is R-3 and replacing it with R-6 in a spot that doesn't have a lot of space to blow new stuff in you could be short changing yourself if you don't have the old stuff taken out. If there aren't any space concerns and the guy sealing from below or moving stuff aside is careful, adding it to the top isn't going to hurt anything.

Thanks for the reply Matt.

They are calling the existing FG "Chopped FG". Apparently a product that was used for a period back in the 70s. Neither of them had any concerns about space except at the very edges of the roof where it will be a little tight. Both have said they would blow in cellulose and one said he could do either blown in cellulose or FG. I'd say that the max depth of the existing is about 6-7" in spots - obviously some spots are lower.

The stuff has been up there for quite some time. One of the guys found a dead mouse and I'm sure there are other critters, dead and alive, up there as it hasn't been touched in 30+ years (aside from pushing it aside to put in cans). That alone makes me think I should just rip all the old stuff out and start anew...

Again, thanks for the replies guys...

 

[peakbagger]

In order to judge the effectiveness you can require a pre and post air test with a blower door. A good contractor can work around the old insulation. There is no issue in putting new insulation in over old. Realistically if there were critters up there before they will get back in there again in a few years but that is your call.

A general comment is that ice damming frequently is caused by blockage of the soffit vents not inadequate insulation. Make sure that the contractors put in proper vents in all the soffits and review your attic ventilation

 

[Nelson]

In order to judge the effectiveness you can require a pre and post air test with a blower door. A good contractor can work around the old insulation. There is no issue in putting new insulation in over old. Realistically if there were critters up there before they will get back in there again in a few years but that is your call.

A general comment is that ice damming frequently is caused by blockage of the soffit vents not inadequate insulation. Make sure that the contractors put in proper vents in all the soffits and review your attic ventilation

I di have a blower door test done as part of a "mini" energy audit. I was running about 2600-2800 CFMs. House is approximatley 3600 sq ft ranch with finished exposed lower level. I was messing around trying to convert that to ACH and I think it came in around 4 or 5. Either way, I think there is definitely room for improvement.

Agreed about the attic ventilation. Between warm air from the house leaking in to the attic and probably not enough ventilation, you have your recipe for ice damming. The ventilation isn't horrible but it could be better. I think some of my soffit vents are blocked with insulation so we will fix that when the attic gets done...

 

[ihookem]

You most likely have a house with a 4-5 pitch roof and a heel of 3" above the wall. This means the space between the roof sheathing , or plywood and the top of the wall is about 3". The more the better for more insulation. In these cases, you need to foam shut the area between the top of the wall and the roof plywood. You will need some ventilation in every 3 spaces. I think that is still code in Wis. Make sure the contrator sprays foam underneath the shingles for about 5-6' up in between the roof rafters. Spraying the top of the drywall a few feet back will help too. This is what keeps the dew point away and keeps ice daming form happening. I have done this several times but with regular 1" foam. It works well but closed cell spray is much better. You will notice a warmer house that same day if done on a cold winter day. Ya can keep the old insulation in if you want. It still has R value. Then blow in at least another 16-20" of cellulose. You will have a true R 60 ceiling. The can lights ,, I don't know if you can spray foam them or not. I didn't do mine but are buried with 20-22" ins. in the attic. Have them ( or you spray foam the basement floor joist cacities too. Insulation is a lot cheaper than paying propane bills for the life of your house.

 

[Nelson]

You most likely have a house with a 4-5 pitch roof and a heel of 3" above the wall. This means the space between the roof sheathing , or plywood and the top of the wall is about 3". The more the better for more insulation. In these cases, you need to foam shut the area between the top of the wall and the roof plywood. You will need some ventilation in every 3 spaces. I think that is still code in Wis. Make sure the contrator sprays foam underneath the shingles for about 5-6' up in between the roof rafters. Spraying the top of the drywall a few feet back will help too. This is what keeps the dew point away and keeps ice daming form happening. I have done this several times but with regular 1" foam. It works well but closed cell spray is much better. You will notice a warmer house that same day if done on a cold winter day. Ya can keep the old insulation in if you want. It still has R value. Then blow in at least another 16-20" of cellulose. You will have a true R 60 ceiling. The can lights ,, I don't know if you can spray foam them or not. I didn't do mine but are buried with 20-22" ins. in the attic. Have them ( or you spray foam the basement floor joist cacities too. Insulation is a lot cheaper than paying propane bills for the life of your house.

Great advice on the rafters and top of the drywall at the edges.. Both contractors have spray foam machines so it shouldn't be too much of an issue to foam the top of the drywall and rafters a few feet in.

For the cans, they have a "hat" they can put over top of them and spary foam them in place. Had I not already replaced half of them with LED lights, I would have gone the LED retrofit route. I did a few in our master bath with the retro fits and the infrared scan couldn't even tell they were there.

Looking forward to buttoning up the top portion of this house and seeing how much of a difference it makes. I am also having one of the contractors come in and do the small amount of box sills we have exposed in the basement (~50 ft worth). They are going to do it for $350 which I think is a great price. It would likely cost me more to do it in terms of materials and labor.

Depending on what the second quote comes in at, i'm leaning towards leaving the existing insulation in and just having them work around it.

Thanks again for all the replies! Next project is working on my stove set up so I can further minimize my propane usage!

 

[Nelson]

Summer came and went... but the time for doing the attic has arrived. I had a respectable contractor out this week to do the work. Here is what we had done

1. Air sealed top plates
2. Foam board out toward the eave area plus "rafter shutes" every 4 feet or so
3. Foamed up the canned lights - I have a few that were out toward the eaves that he did the best he could (likely working in less than a foot of space due to the slope). I'm going to do LED retrofits on those just to be safe
4. Foamed around all appliance vents (bathroom fans, stove fan, etc)
5. Ducted two bath fans out through the roof - prior to this work, they were just venting out through the eave vents (flexible liner just laying out by the eave vents)
6. Blown in cellulose to ~R50
7. Installed new bath fan in master bath with motion dector and can run continuously. Right now, we have it set to run at 40 CFM all the time. Goes up to 80 CFM when motion is detected.

After the work was done, prior to blowing in the insulation, we did a blower test. Down to 1800 CFM from ~2800 CFM in the spring. Pretty happy with those results. We also walked the house with a smoke pencil while the blower test was running. Most of the canned lights checked out great. As expected, the cans near the eaves were still just a little bit leaky due to the fact that he had a hard time getting back there to foam them. Will put LED retrofits in those. Outside of that, a couple of doors were a little leaky but everything else looked great.

With a 3600 sq ft home, the 1800 CFM gets me to an ACH of 3.75 which, according to what I have read, is actually a little below where you want to be without mechanical ventilation. Master bath fan should help with that.

All in all, I'm very happy with the results. Seeing positive results in regard to heat retention. House also "feels" tighter.

Put the new PE Summit this week as well so I'm ready for whatever this winter has to offer!

 

[woodgeek]

Sounds like a fantastic job. Many airsealers are happy with a 20% reduction, or getting to 6-7 ACH.

RE the ventilation, I have been at ACH50 = 5 for a year and a half now. I don't need the extra ventilation in the winter (calculated stack effect is closer to 100 cfm). It was getting a little stuffy at times in the spring and fall, mostly when there was no wind, as you might expect. I just cracked a window the first summer/fall, and that helped. The second summer I set up a timer to cycle one bath fan in the spring/summer/fall. I ran it at 50 cfm, and I decided that that was a little too much (pushed the RH up more than I wanted during humid weather).

You'll experiment, but I think the 40 cfm is just a waste of energy in the winter, while you will be glad to have it during the other seasons. If it is 20°F out, the BTU load is 1.08*40*(70-20) = 2100 BTU/h, or 50 kBTU/day or maybe >5 million BTUs/season.

It will also be interesting to see how hard the place is to humidify in the winter...in WI I don't suppose you will want to go too high in RH. I think cooking and showering (w/o bath fans in winter) gets me most of the humidity I want...and a small humidifier maintains the whole place at 30-35%RH.

Enjoy your new house.

 

[Nelson]

Sounds like a fantastic job. Many airsealers are happy with a 20% reduction, or getting to 6-7 ACH.

RE the ventilation, I have been at ACH50 = 5 for a year and a half now. I don't need the extra ventilation in the winter (calculated stack effect is closer to 100 cfm). It was getting a little stuffy at times in the spring and fall, mostly when there was no wind, as you might expect. I just cracked a window the first summer/fall, and that helped. The second summer I set up a timer to cycle one bath fan in the spring/summer/fall. I ran it at 50 cfm, and I decided that that was a little too much (pushed the RH up more than I wanted during humid weather).

You'll experiment, but I think the 40 cfm is just a waste of energy in the winter, while you will be glad to have it during the other seasons. If it is 20°F out, the BTU load is 1.08*40*(70-20) = 2100 BTU/h, or 50 kBTU/day or maybe >5 million BTUs/season.

It will also be interesting to see how hard the place is to humidify in the winter...in WI I don't suppose you will want to go too high in RH. I think cooking and showering (w/o bath fans in winter) gets me most of the humidity I want...and a small humidifier maintains the whole place at 30-35%RH.

Enjoy your new house.

I concur RE: the 40 CFM fan. I'm concerned about the heat loss and what benefit it is providing. I'm going to try and use my nose to figure out how quickly the air changes are occuring (how long do cooking smells linger). So, yeah, definitely going to play around and experiement.

So far, we've been at 30-35% RH throughout the hosue and we've been in the teens for highs all week. I can live with that. I don't want to have to deal with mechanical humidification. Like I you, I plan to use showers, etc to pump a little moisture in the air if it starts dipping below 30%.

 

[Wildo]

Glad to hear the results! It sounds like you will be a lot warmer this winter. I too had similar problems last winter that ended with mold remediation and spray foaming the entire house over the summer due to blocked venting. The difference here is amazing we have burned 1/2 cord of wood and 3 gal of K1 vs. ~2 cords and 20 gal so far, you will most likely see a pretty fast ROI depending on initial heating and cooling costs and post work heating and cooling costs. If LP prices go crazy again this winter your payback will be even faster. Best of luck and stay warm.