Professional or DIY attic insulation

[Monkey stache]

My attic REALLY needs insulation and I wondering if I should do it myself or have it done professionally. The reviews on homedepot.com say it's really easy and I'm confident I can do it. My gas provider offers a 30% rebate if a professional does it so I got a couple of free estimates. One company said I need 2 turbine vents and air chutes for proper ventilation. Does that sound right or are these upsells they're tacking on?

My house was built in 1920, the attic is only 300 square feet of crawl space, and I'm in Minnesota so snow dams are a concern (haven't been a problem so far). If I ONLY insulate the attic myself it should be around $300-400 (for R50). The professionals want about $2k (!!!!) for R50 insulation, air sealing, air chutes, and 2 turbine vents. I get about $300 of that back in a rebate. Is it worth it? Will I avoid really expensive problems like ice dams or are they just trying to get money out of me?

[Jeremy E.]

http://www.mrmoneymustache.com/2014/05/01/beating-the-stock-market-with-diy-insulation/

[Monkey stache]

"**Airtight houses still need ventilation. In the olden days, houses were so leaky that you’d get more than enough fresh air just through the cracks. Modern houses fixed the leaks, but that caused indoor air to become stale"

That's from MMM's article. Sooo my house is old and leaky so don't air seal and add ventilation?? Just insulation?

[MDM]

That's from MMM's article. Sooo my house is old and leaky so don't air seal and add ventilation?? Just insulation?

Need to distinguish between the living space and the attic. 

If you do a reasonable job caulking, weatherstripping, etc. to reduce air leaks into your living space, that is a good thing - and, given the house age, there will likely still be enough air infiltration to avoid stale air.

You want outside air to enter your attic under the roof edge, then exit the attic as close to the top (e.g., a ridge vent) as possible.  This keeps the roof cool in summer (obviously good) and tends to keep the entire roof at ~the same temperature (whatever that temperature is) in the winter.  Ice dams form when the upper part of the roof is warm but the lower part is cold: snow melts above, then the melt water freezes below.

[Monkey stache]

I've lived in this house for 4 years and moisture and ice dams have not been an issue. Does that mean the ventilation is fine as-is? Will adding insulation change the need for ventilation? Can I add insulation and keep an eye out for warning signs of ice dams and add ventilation later if needed?

[JRA64]

I had air sealing and extra insulation added to my attic a few years ago. Before I get into what I learned when I was researching it, let's talk about ventilation, as there are two different air flows to considered.

The first is air flow from the outside, into the attic area through soffits, and ultimately out through the ridge attic vents. This continued flow of cold air keeps the roof cold, prevents the snow from melting and draining to a lower, colder location on the roof and re-freezing, which builds ice dams. When you add insulation to the attic, sometimes it blocks the soffits and decreases this flow of cold air. If this happens, you might have more problems with ice dams. This may be why they are talking about air chutes. If you haven't had problems with ice dams, you currently have adequate ventilation and I'd question the need for turbine vents.

The second air flow is the warm air in the house, which can flow into the attic through small holes (or not so small) around light fixtures, seams around walls and in the boards that make the ceiling, etc. This rising warm air is bad for a couple of reasons. First, the hot air escaping into the attic can melt snow on the roof, leading to ice dams. The hot air your house loses is replaced by cold air, which your furnace heats. When the house loses warm air into the attic, the house feels drafty. Air sealing is intended to minimize this flow hot air from the house into the attic.

My contractor explained it to me by comparing it to dressing for cold weather. Insulation is like a polar fleece. While it provies warmth, a cold wind will go right through it. Air sealing is like a windbreaker. You're warmest if you have a layer of each, rather than just a fleece or just a windbreaker.

I ended up getting both air sealing and the insulation. The crew wore respirators while doing the air sealing, which convined me it was not a project I wanted to do myself. I noticed some improvement in my heating bills, and a big improvement in comfort, even in the summer. There used to be a 10 - 15F temperature difference between the first and second floors in the summer. The upstairs is much cooler in the summer now. I didn't turn my AC on even once this summer.

[Papa bear]

I assumed that you were going to insulate the floor of your attic with either blown in or batt insulation.  However, with a contractor suggesting air chutes, were you planning on insulating directly to the bottom of the roof sheeting?   That is an entire different way to go here and would require air chutes for ventilation depending on what type of insulation you use. 

More info please!

If you go that route, are you spray foaming? Open or closed cell? Batt fiberglass?   It is a truss construction or ridge beam and joists?  24 or 16 on center?  Dimensional or nominal 2 x ??'s? Can you get r50 with fiberglass?




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[Monkey stache]

I assumed that you were going to insulate the floor of your attic with either blown in or batt insulation.  However, with a contractor suggesting air chutes, were you planning on insulating directly to the bottom of the roof sheeting?   That is an entire different way to go here and would require air chutes for ventilation depending on what type of insulation you use. 

More info please!

If you go that route, are you spray foaming? Open or closed cell? Batt fiberglass?   It is a truss construction or ridge beam and joists?  24 or 16 on center?  Dimensional or nominal 2 x ??'s? Can you get r50 with fiberglass?

Maybe that's the direction the contractor is going to increase $$? That's not what I wanted though. All I want to do is insulate the floor of the attic without causing bigger issues down the road. If extra ventilation isn't needed I'm going to do the air sealing myself and do blown in insulation with a machine from the hardware store.

Edit: The way I worded this sounds like I already agreed to the work. I haven't. Just a free estimate.

[Emg03063]

Do your own air sealing with great stuff.  Use the orange for any electrical penetrations; white for top plates.  Leave the exterior top plates unsealed.  Staple these things to the inside of your roof at the soffits to keep them from getting plugged with blown insulation:  http://www.homedepot.com/p/ADO-Products-Durovent-23-1-2-in-x-46-in-Attic-Ventilation-System-with-Built-In-Baffle-10-Ctn-UDVB234610/202389935?cm_mmc=Shopping%7CBase&gclid=CKWS6qLun8gCFQuUaQod-d4GxA&gclsrc=aw.ds

[Monkey stache]

Update: I was all ready to do this myself and then I noticed knob and tube wiring on the attic flooring which will burn the house down if I insulate over it. That's something I'll have to leave to the pros. And to think both insulation companies were just going to insulate over that and create a major fire hazard! *SIGH*

[Emg03063]

Is the knob and tube wire live, or is it just legacy wiring that wasn't removed?  Depending on how long you're owned the house, your home inspector should have flagged any live knob and tube wiring when you bought the place.

[Monkey stache]

It's definitely live because I checked with a voltage detector. Our home inspector said nothing about the wiring. *ssiiigghhh*

[szmaine]

I had knob and tube as well. It will definitely have to go. The good news is that you don't have to do the whole house but can just get the attic cleared.
You definitely could do the air sealing yourself with spray foam and a respirator is a good idea anyway...you could also get a quote from someone for the air sealing and vents alone and finish with the insulation yourself. Perhaps that will save you money over all since you have to pay for knobe and tube removal. Mine was $1600 for 1 day/ 2electricians but I also had a co2/smoke detector installed. Not a bad idea while you've already got them on hand and don't have one already.

Sorry, old houses are a bit of a money suck sometimes. Either way do the insulation anyway, you should see a big comfort difference.

The house isn't post and beam is it? If so it will be impossible to install soffit venting. Im just wondering why you have only 300 square feet...do you have a sloped ceiling and kneewalls?? If so they should really be done too.

 My house just has a screened passive vent in each gable end.

[Monkey stache]

The house is only 950 square feet and it's a one and half story home. One of the contractors I got a quote from said the attic was 300 sq ft at most. I googled post and beam house and I don't think it is since the attic is a separate crawl space. I think I'll have the electrician leave the old wiring since that's less work (less money!) and it's not a fire hazard if it's disconnected.

[justajane]

We have a 1920s home with an attic crawlspace. Blew insulation in it before we heard that doing it on top of knob and tube wiring was a problem. I have no idea if it is live or not. 8 years later we are still alive. We contacted an electrician who told us not to worry, as did the fire chief of our local fire department. I'm not saying you shouldn't take care of it first for your own peace of mind, but many people told me the risk is overblown. In general, the risk of knob and tube wiring appears to be overblown.

Also, our home is 1000 sq feet and we paid professionals $400 to do it 8 years ago. And this included cutting a whole in the drywall/plaster/lathe ceiling to create an entry point.

[Monkey stache]

I've read similar things online but I've read the opposite as well. I don't think I'd forgive myself if I knowingly did something that burned my house down. With that said the old wires have had insulation over it for 95 years and hasn't burned down. But that's just a few inches of insulation  so I'm concerned if I add more (R50) it might change things.