Insulating attic plans

[midnight armadillo]

It looks like we'll be going ahead and adding additional insulation to my mother-in-law's attic. The house is freezing in the winter and broils in the summer. IT's got your standard 1970's construction. The attic looks to have 4" of fiberglass in rough shape for R13 total...not counting pulled up areas,etc.

The first task will be to fix drafts around the house, add gaskets to outlets, etc. That's easy enough and my MIL and SIL can take care of that. The attic is 20'x40' or so. I'm thinking we'll put 2x8's crosswise to the joists and run them down the center 16" on center. Then blow in 8" of cellulose insulation everywhere (after adding soffit vents). An 8' run of 5/8" particle board down the middle over the 2x8's will finish it off.

Finally, I want to get her an attic stair cover box made of rigid insulation. I gotta find that website somewhere...

You know, I think I need to add a pair of bathroom exhaust fans too. Neither upstairs shower has one and she had trouble with icedams in past years. The new roof has a rubber membrane to prevent them but I think the cause is the shower moisture. I should do this first BEFORE I add insulation everywhere :-)

Total cost for 8" of insulation, going from R13 to R38: ~$200 for the cellulose, with a free blower rental from Lowe's since it'll be more than 25 bags.
$50 for a bigass truck rental. ~$200 in lumber costs, maybe more? ~$100 for the attic door cover (I know I could make one, but this'll be enough work as is). $550 total should do it. Plus the exhaust fans. One day for the fans, one for the insulation. Oh, and more money for the safety equipment (goggles, respirators, etc), and for a case of quality beer to bribe a friend to help. And the money for the soffit vents.

Last year she was spending $100/month on heat, with it set at 62 deg! This year it's up to $170 after prepaying to lock in a lower price. I suspect this project will pay for itself in one or two winters. ACtually less for her since I'm paying for half ;-)

Any comments, anyone? Did I miss anything glaringly obvious?

[Carolab]

1. Get some space heaters

electric ones. They're cheap and will provide backup.

[MADem]

2. HOW ARE HER WINDOWS???

Don't neglect those, they can account for a shitload of heat loss. If they are horrible, but you can't afford replacements, get those temporary systems made of flexible thin plastic sheeting that are installed with two sided sticky tape and a hair dryer. They are cheap, and they do make a real difference. Also, check door weatherstripping too--either replace or get one of those cutsey sand filled draft blockers for all doors leading outside.

Do the exhaust fans first, though, then the insulation, then all of the small stuff.

[BillZBubb]

3. A stairbox cover is easy to make.

I bought some rigid foam insulation (4x8 sheet) with a reflective side. Cut the pieces for the sides and top with a box cutter. Glued it together with hot glue. Then caulked every joint for a little extra support.

It doesn't get much abuse and has worked well for me for over 4 years. And it was inexpensive.

You also might consider adding an attic ventilation fan as well. Lowe's has those. The thermostat allows you to set at what temp it comes on. They run about $70. I have mine set at 105 degrees and it has cut my summer electric bill by about 8 percent--and the house just generally seems cooler. Here in Texas, 8 percent on an electric bill is pretty decent savings! You will have to wire it and cut a hole in the roof, but it sounds like you have some experience with this sort of thing.

[midnight armadillo]

6. Attic fan

My MIL actually has an attic fan. She doesn't use it and has it blocked off in the attic. Why? The wind somehow blows the louvres around and makes loud banging noises at night. <sigh> Maybe next summer I can replace the louvres or the whole darn thing. Attic fans kick butt.

Unless you mean a fan just for the attic, not a whole house fan. I found a solar powered one (www.realgoods.com) that fits in the gable-end vent for easy installation - you just need a little solar panel on the roof. I'm not sure if they're worth the effort in the MA climate. Maybe I'll try this next summer too, depending on the comfort results of the attic insulation.

[Dogmudgeon]

4. How does Kevlar rate?

I used to work at DuPont, and they were very high on Kevlar there. Claimed it was superior to fiberglas. Any experience with it?

--bkl

[midnight armadillo]

5. Group reply

Windows: they're alot of single-pane junk. Some are drafty, and we'll definitely put up some of that plastic sheeting on them. I'd like to pull off the moldings and insulate the gap between the window and the framing, but that's probably more labor intensive than we want to get this year.

Kevlar: no, I can't say I've considered it - we just need to stop heat, not bullets ;-) Some countries (Ireland, New zealand) use wool due to their sheep surplus.

Attic box: Good idea on how to build one! How did you seal the bottom? Magnetic tape? I had figured it would be more work than than. A 4" thick box would be good for R15 or so, not bad! Lowe's has that Reflectix insulation to add on top which would help too.

[Kolesar]

7. Are the new 2x8s to be installed so that you can put a floor in?

I presume that you are going to put in an attic floor for storage.

If you don't need the storage, you could just put some boards down the center for a walkway and start installing insulation. You could blow in cellulose or roll additional insulation on top. I still like the Miraflex product. Roll out a few inches of unfaced insulation along with the joists, then roll miraflex crosswise. If the existing insulation is close to the height of the joists, just roll the Miraflex on. I have noticed that 3.5" thick unfaced insulation is not often stocked.

About attics:
http://owenscorning.com/around/insulation/project/addinsultoattic.asp

Miraflex:
http://owenscorning.com/around/insulation/products/miraflex.asp
It is like a comforter for your attic!

My heat calculations at $8/MCF gas with an 80% efficient furnace:

R Area Heat-loss Cost/year
38 800 2,880,000 $29
13 800 8,400,000 $84

She can save $55/year

I think your infiltration remediation project is going to yield more than that in savings, by the way.

[midnight armadillo]

8. yes, the floor is for storage

The floor will be for storage space - the back of the garage is filling up ;-)
My wife & I store baby clothes our son has grown out of and such at my MIL's.

The blown cellulose is definitely somewhat more of a hassle than Miraflex, no argument there. I still like it due to its lower embodied energy (recycled newspaper), void filling, and greater fire resistance over fiberglass. I'll do a cost comparison before actually purchasing, to see if there's any big advantage either way.

The house has oil heat, with prices running at $1.80+/gal in Mass. right now. With 138500 BTU/gal, from your chart there I estimate she'll save $88 a year with her new furnace which is 85% or efficient, I believe. Oil prices are only going up, of course! There is a biodiesel supplier in Mass. that I may get around to calling to see what their prices are like for next year.

[Kolesar]

9. I have a remodeling book with a design for attic-trolley cars for storage

You build train tracks across the length of the attic and little flat bed cars that ride on the tracks. They are coupled together, and you move them with a system of ropes and pulleys at the end of the house. You can have your own little train set in your attic, with the "loading station" being at the scuttle. It was quaint and techno at the same time.

I have a house with a low attic and I have to get myself into the mindset of having a "useful" attic such as your mother's.

[Kolesar]

10. We had a "blower door evaluation" for infiltration & a low budget hint

The analyst put a special rig in the front door that sealed the door then drew a powerful vacuum on the house. We could feel air leaks in a few places. He had a hand held pressure meter that he could hold near openings and determine if there was infiltration because the pressure reading would go up.

There is a low budget way to find infiltration. When you see spider webs and cob webs near the outside of the house, it means you have infiltration. The spiders build near there, because there is a hole and that is a place where tiny insects come into your house. The spider just traps them coming in!