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As some of you know, my family recently moved into a "new to us" home. I have been working on the place for the last month or so and the next item on the list is insulating the crawl space and attic. The crawl has no insulation and the attic has about 4-6 inches of blown stuff. I think I'll start with the attic first since that will probably offer the best return on investment. Has anyone here blown attic insulation before? What should I go with, fiberglass or cellusose? R-Value?

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92 Miata 1.9L naturally aspirated. SSM 21

Just my opinion here but if you already have insulation in the attic and a limited budget why not address other issues like windows and doors that might not be energy efficient? Weather stripping is cheap and works well. Decent replacement windows are not terribly expensive if you shop around at the building supply places like Guy C Lee or Stock Builders. If you can install your own windows you will save even more.

I'd also think a few rolls of fiberglass insulation in the crawl would be a good idea. I'm suprised there isn't any under the house now. How old is this house?

Let me know if you need some new flooring.

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BenchWarmer Motorsports

another one of those damn LeMons heads

just another Chump

we are an Autocross Club Dammit............

Thanks for the flooring offer, but I just did a ton of work with new hardwoods and finishing/re-finishing before we moved in.

Windows are in good shape. I can purchase the insulation for the attic from Lowe's or Home Depot and they loan the machine to blow it at no cost, so for $300-$600 (depending on the R value) I can significantly improve my attic insulation. After a little more reading, I am leaning toward the cellulose insulation since it has a better R-value for a given thickness and does not contain itchy fiberglass. Has anyone else worked with this stuff?

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92 Miata 1.9L naturally aspirated. SSM 21

Its utterly amazing what a difference a $7 roll of weatherstripping can make. This summer I sealed up two exterior doors with cheap weather stripping, month over month it saved nearly $100 in A/C that was escaping around seemingly small cracks. It wasn't a completely scientific experiment, but the weather wasn't significantly different month to month and there weren't any other significant changes. I could immediately tell the difference with my hand pre/post weatherstripping. It just boggles my mind that this house existed for decades without it, think about all the lost energy over all that time air conditioning the outdoors.

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'07, '08, '11 Autocross VP
'06, '10 Mike Dishman Cup
'21 MX5, '13 Corvette GS, '92 Corvette 383 c.i. 413whp/390wtq, '03 Expedition

My brother and I put some of the cellulose blow-in stuff in his attic in a ~1930's house in Durham. It wasn't that hard, you really do need 2 people, one in the attic and one down below to keep the hopper full of insulation and make sure it feeds OK and doesn't clog up.

The person in the attic will get covered head to toe with the dust, it will be in every crevice of your body- but it's not too hard to wash out and like you mentioned, it's not itchy like fiberglass.

My next door neighbor runs a business doing house inspections (he is an architect by training). We were talking about similar stuff and he was also talking about how much he sees lost via poorly sealed electrical outlets and especially in recessed lighting in ceilings (particularly those that are in the attic). The ceiling lighting can act like a chimney and you can have a lot of loss in those if they are not installed or insulated correctly.

Also... before you tackle the crawlspace, make sure that you do your vapor barrier correctly. I have pretty strong opinions on crawlspace vapor barriers and I think it is VERY easy to get bad advice online and even from contractors who "have just been doing it that way for years" (and doing it wrong). My favorite is those who place plastic down, but leave gaps around the edges (near walls, or support posts) to "allow the ground to breath". It "breaths" all right. It exhales a huge amount of moisture into your crawlspace. Exactly the opposite of what you want.

Good luck!

Richard

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Richard Casto
1972 Porsche 914
2013 Honda Fit Sport
2015 Honda Fit EX
http://motorsport.zyyz.com
Money can't buy happiness, but somehow it's more comfortable to cry in a Porsche than a Kia.

Yeah, forgot to mention before, my Raleigh house has the cellulose stuff in the attic, applied very thick. My power bills indicate it worked exceptionally well, but damn if it isn't messy, very dusty, but at least it isn't itchy like fiberglass.

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'07, '08, '11 Autocross VP
'06, '10 Mike Dishman Cup
'21 MX5, '13 Corvette GS, '92 Corvette 383 c.i. 413whp/390wtq, '03 Expedition

Great input, thanks guys. I am not looking forward to the dust, but I still think cellulose is the best option for this home. As for the crawlspace, I have been reading about sealed and conditioned crawlspaces. It looks like I could do this myself for around $3k. Anyone have one?

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92 Miata 1.9L naturally aspirated. SSM 21

Mine.. I would call "Partially" sealed. It is ventilated. But otherwise I have the floor sealed up to the walls and pillars. Even with the outside vents still functioning the humidity level is much lower than before. I think sealed and conditioned is a great idea.

One thing to mention is that I have seen in more than one house where they have at the lowest point some type of drain pipe that runs from inside the crawlspace to the outside (typically to the drain system that runs around the foundation). This pipe usually is at the lowest point in the crawl space and is buried under gravel. The idea is that if you have some type of water in the crawlspace (flood, whatever) that it will drain out via that path. But I have also seen where the pipe that drains this into the yard or somewhere else get crushed and it slows or stops the ability to drain away from the foundation. And then when it gets really wet outside (heavy rain with saturated soil) the water reverses flow and comes back into the crawlspace. In short, before you seal it up, maybe sure you don't have a way for ground water to get in, or if you do, that you make sure it drains properly.

Richard

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Richard Casto
1972 Porsche 914
2013 Honda Fit Sport
2015 Honda Fit EX
http://motorsport.zyyz.com
Money can't buy happiness, but somehow it's more comfortable to cry in a Porsche than a Kia.

I rented the machine and blew a bunch in. It's easy like everyone said and you just need to keep the hopper filled. I think I might have a block of it in my garage I didn't use. I'll check and you can have it.

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1990 Faded Reddish CSP Lite Miata
2002 Electron Blue Corvette Z06
2005 Mazda 6 Wagon
2003 Nissan Pathfinder DTV (Dog Transport Vehicle)

We've "closed" our crawl. Blowing insulation is probably first as a better bang for your buck and time.

But - before you do either, make sure you seal all the penetrations both in your attic floor and your crawl ceiling. This is important because of the stack effect and air filtering through your house. Insulation only meets its rated "R" value in still air. The cans of expanding foam sold by HD, etc. work fine for this. Be careful in the attic. Sheetrock doesn't support much weight - yep I had a ooops there so we started contracting a good part of this.

We followed this path:

- Sealed the floor/attic penetrations.
- Blow additional cellulose in attic to upgrade to R42 or so (an additional six inches in our case)
- Closed/conditioned our crawl - Removed R19 from underfloor. Closed cell spray foam on the walls to R14. Ground poly sealed to piers and walls. Provided one positive close air duct in the crawl space for dehumidification. No air return. Not technically "sealed" because we run a slight positive pressure but we followed the code. We have a remote temp/humidity display from our crawl so I can monitor things.
- Our most recent project was a couple of geothermal heat pumps this spring. They sure look pretty sitting it that clean white crawl space.

Frank

So this past weekend Monica (my wife) and I blew 70 bails of insulation into our attic. We used the cellulose stuff, so it was dusty, VERY dusty. Total depth is around 14 inches to allow for some settling, so I should have an R value around 38 now. Lowe's lends the machine for free when you buy at least 20 bails, so our total cost was just shy of $700. Prior to the insulation, when the outside temperature dropped into the 40's the furnace would run non stop. Now it cycles on and off like it should.

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92 Miata 1.9L naturally aspirated. SSM 21

I have a couple of concerns about sealing the crawl. The first is draining any moisture, I probably need to wait a season or two to figure out if it gets wet down there. I dread the idea of trenching the perimeter and adding a French drain. I guess some things are worth hiring out

My other concern is the furnace combustion intake. I guess if you have a newer high efficiency unit, you can run your intake and exhaust with pvc pipe to outside. What should I do with an older furnace located in the crwal that intakes from the side of the unit? It's probably not the best idea for it to source intake air from a "sealed" crawlspace.

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92 Miata 1.9L naturally aspirated. SSM 21

I would definitely make sure the ground is relatively dry first. Our builder installed a french drain around the perimeter and the dirt was pretty dry under the poly before we closed the crawl. The problem in NC is that the dew points in the summer are often around 70F overnight. In a vented crawl this outside air creates higher humidity and potential condensation in the relatively cool crawl space even without ground moisture.

It's also helpful to have a drain to the outside from your crawl space. Especially if your water heater is there.

Here's a good link to cover the issues with combustible appliances. The folks at Advanced Energy did much of the research around closed crawl spaces.

http://www.advancedenergy.org/portal/cr ... erence.pdf

I'll note that my empirical measurements as well as research papers in Building Science indicate that relative humidity readings need to reach at least 85% before you run the risk of mold forming on framing limber. Plywood is even slightly more resistant. So, imho, no need to dehumidify to the 50-60% range as some (mostly dehumidifier manufacturers) claim.
We've been fine with an HVAC vent with a positive close damper off the crawl air handler.

Frank

In regard to the crawl space, we have Terminix service the house for bugs. Part of their inspection is checking for moisture under the house. A few years ago the tech said I was getting dangerously close to reaching the max moisture content under the house. Coupled w/ that I was starting to get some of the white mold on major floor joists. My crawlspace at the time was exposed dirt and I opened and closed the vents depending on the season. Their recommendation was to cover the floor w/ a heavy mil plastic and keep the vents closed. They didn't mention sealing them per say.

After covering the dirt and closing the vents, the next inspection showed the moisture content dropped dramatically. Terminix was happy, so I was happy.

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Rodney

'08 Bullitt mustang, CAM 7
Autox VP '09-'10, President '11-'12, interim President 2nd half of ‘14
proud recipient of the Bowie Grey service award '12
Now just a guy driving a mustang....