Insulation (update)
 

I did a search and read the prior insulation threads, and the insulation part of Pookie's attic fan thread.

We had a home energy audit because our electric bills are both high and the same throughout the year (we have gas heat, so the bills should be higher in the summer).

The largest item on the audit, likely the most helpful, but the most expensive estimate-wise is to improve the insulation in our attic.

I'll go into the specifics first, and then post my questions:

Currently, we have 4-6" of cellulose insulation, going to the eves (no baffles), not sealed on the tops of the walls (suggestion to do that in the report with baffles) and without covers on the recessed lighting allowing significant airflow through the light fixtures.
There is also installed 3/4" plywood "flooring" (4x8 sheets) through about 1/3 of the attic, going end-to-end (approx. 70 feet) and the width of the bottom of the W-shaped rafters (8 feet).
There was also significant leakage around the drop-down door.
There are 2 sky tubes which are neither sealed nor insulated, and 2 bathroom vents which are also not insulated (one is a single fan remote fan drawing two low-noise vents and would be very difficult to insulate other than insulated flex tube, and I don't want to make Jesus cry).
There are vents (about 2 x 2.5") at either end of the attic, plus when we recently replaced our roof, we installed a ridge vent running the length of the attic

The recommendations are;

• Seal accessible top plates and end walls with foam
• Seal and insulate sky tubes
• Seal all penetrations through attic floor (plumbing, etc.) with foam
• Install covers on recessed lights so the are insulation compatible and airtight
• Insulate to R49 (16" of insulation) with fiberglass or cellulose
• Install baffles so the eave vent air goes over the insulation
• Install an attic tent over the door
• This would involve installing 2x6's and raising the flooring to accomodate the added insulation

Questions:

1. Is there denser insulation available to install beneath the flooring as I'd hate to lose 5" of height (I'm pretty tall...)?
2. How much insulating value is the 3/4" plywood itself?
3. Is the attic tent a good solution, or would the experts here weatherstrip the door?
4. How much of the above can I do myself relatively easily? The estimate is quite a few sets of Hoosiers worth!
5. Is this a job I should just plunk down the money because it's hot as blazes up there and much of it is a crappy job, or is it one of those things like changing brake pads -- "I can't believe I paid somebody that much to do this job?"

Peter: several years ago, we had another foot of blown-in cellulose insulation added to the amount originally in the house (12 inches? 8?) plus the necessary baffles and and increased number of eave vents. It's difficult to describe the difference that made. Not only is the house warmer in winter, cooler in summer, it's also much, much quieter from street noise and storms. I don't remember it being particularly expensive. My wife reports that heating/cooling bills have been noticeably less.

Thanks, Richard. Because of the floor needing to be raised, we're being quoted thousands of dollars.

I had a different thought - what do people think of insulating the inside of the roof to, like, R39, and 6" of insulation on the floor surface? I got this idea reading the installation instructions for the soffit baffles, which gave 2 options.

Peter

If you don't use the attic for storage you don't need the plywood and because of that the raised floor. Can't believe you actually use the attic other than stashing stuff in it

We use the attic for storage. Old records, boxes from just about everything we own (unfortunately, boxes from lots of stuff we no longer own - need to clean that out). Off-season stuff like hammock, market umbrella...

Expensive storage

Yes, but law requires maintenance of medical records for many years. Almost all of what I would actually need is in my computer (and backed-up to 2 sites) but since it's not 100%, and scanning what is missing would require scanning everything there ($$$$$$), that is not an option.

But given that we have to insulate for many reasons, can anyone answer any of my questions? I believe I have the answers to some:

1. Denser foam insulation is about 1"=R5 (so for our desired R49, about 10"). And, that is much more expensive than blown-in or fiberglass (would need 10" x 500 sq. ft.).
2. Plywood isn't going to be enough of an effective insulator to make a difference.

Therefore, if we want flooring, we're going to have to raise it.

But how about the other questions? Thanks in advance. The expertise I've seen on Dorkiphus has been impressive, and I'm hoping to learn more.

Have you considered total foam insulation? Much more efficient than batt or cellulose but more expensive. Mike Holmes of TV fame uses it exclusively in all his home improvement programs. I'm no tax expert, but I would think that this entire project would be deductible as a necessary business expense (storing medical files). Dunno if it's still applicable, but when we did our home there was an appreciable tax credit.

Mike Holmes is in Canada, eh? Their climate is different than ours here in the DC area. They love spraying urethane foam on the bottom of the roof sheathing up there and making 'compact' roofing systems.

The issue with that is if you ever get a roof leak you could suffer a lot of sheathing damage (especially if you have particleboard sheathing) before you even realize you have a leak. The way we typically handle things in the DC area is to leave an air space below the sheathing and circulate air through it, so the sheathing has a chance to dry out some if a leak does occur.

Frankly we have too many cooling days in the DC area for the compact system to be a good idea. That being said, it is getting more popular as people hear about it and see it on TV, although they often do not realize it is not optimum for our geographic area.

FWIW: I've only seen Holmes spray it on walls and attic floors, never on the bottom of roof sheathing. He's a big advocate for adequate air floor through the attics.

Is particleboard sheathing even allowed by code in this area? Kinda dangerous if it gets wet.