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Old 08-04-2015, 10:00 PM   #1
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crawlspace insulation


Hi

I had posted some non-insulation questions in building construction (same pictures). I've been looking on-line about this a lot, and the one and only theme I'm seeing is that it's REALLY easy to screw up the insulation in the crawl space. The house was built in 1976, we bought it last year, and are about 10-15 miles north of Seattle. It's what I've known as a tri-level (I've heard them called split levels too).

The house has some thermal issues probably due to poor (lack of) insulation, and not just in the crawlspace, I'm starting with the crawlspace due to lack of a vapor (or mouse) barrier on the cripple walls (yup that's the backside of the aluminum siding). I will be pulling up the affected siding, only common with the two exterior cripple walls and adding plywood. There is barely any insulation of any kind in the crawlspace, the floors are using 2x10 joists with paper backed insulation (looks like it's meant for a 2x4, not a 2x10, I'll admit it appears much thicker in the picture). The cripple wall shared with the 1st story has newer open faced fiberglass. There are no signs of rot anywhere. There are water pipes (un-insulated, I'm up to that challenge), drain pipes and air ducting (insulation worn out) in the crawlspace.

The thermostat is in the mid-story making it hard for me to gauge how much the crawlspace insulation was working last winter. At this point I'm just looking for general advice and links. I'm undecided whether to DIY the insulation or not.

My last house was built in 2007 and had open faced insulation held in with strings everywhere in the crawlspace. That's what I'm most familiar with around this area.

Thanks in advance for ANYTHING!
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Old 08-04-2015, 11:19 PM   #2
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Do you have access to any conditioned space in the crawl?

How is drainage? Any water issues in the crawl?

Sounds like a good candidate for sealing it up, insulating it, and conditioning it.
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Old 08-05-2015, 07:05 AM   #3
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Thanks for the reply

The one access point to the crawlspace is a door under a stairwell in the cripple wall that's shared with the 1st story. That's a closet, so two doors between the crawlspace and the rest of the house.

Funny you should mention drainage. I've just spent the last 1.5 months re-leveling the ground outside the two pictured walls due to drainage. The previous owners had buried an inch of siding on one side. The other side was where the gutter runoff was being directed, complete with a crack in the footing with no other drain path. I lowered one side by a foot, raised the other side by a foot and laid 55 feet of 3 inch pipe. Fixed three cracks in the footing with Hydraulic cement from the outside, still need to get to the inside. I have yet to find a drain in the crawlspace and suspect there may not be one, but no signs of pooling, or even puddles. The vapor barrier on the ground is worn out due to age, so I will find out for sure one way or the other in the next few weeks.

Of all the houses we looked at last year, and when I bought the first house, I've never seen encapsulated around here. I have seen some pictures on-line though. This was FAR from the worst crawlspace design flaw I saw last year.
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Old 08-05-2015, 01:08 PM   #4
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Add some diagonal 2x4 braces, one in each corner (two req.) and 1 every 20' (code req. 25') for wall lateral shear resistance. Leave the siding alone unless you are replacing it for other reasons. Bracing is allowed on inside. Your thermal barrier is the floor insulation, don't insulate the walls...

No rot at all- is because it is a vented crawl which works fine for our Pacific northwest; http://www.energy.wsu.edu/documents/...ces%5B1%5D.pdf

Some good points; http://www.kenergy.us/pdf/Regional%2...pace_final.pdf

Unless you have HVAC ducting down there and live in the Southeast, notice "comment" by Adam Gloss; http://www.energyvanguard.com/blog-b...re-Not-Friends

I'd fix the insulation, though. Paper goes on top-side around here, unless it's on both sides. Air seal (caulk/sealant) all deck penetrations to stop the "stack effect";http://www.wag-aic.org/1999/WAG_99_baker.pdf Add some housewrap on joist bottoms to protect new insulation (unfaced) from wind-washing by ventilation.

Gary
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Old 08-05-2015, 09:18 PM   #5
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Thanks Gary!!!!

Those were some REALLY helpful links. Those diagrams pretty much show me exactly what I needed. The heating unit is in the garage and does have ducting in the crawlspace to the mid story. The cooling unit is two window air conditioners on the 2nd floor (not powerful enough to cool the whole house). I'm thinking I'm having stack issues in the garage, but that's another post (couple of items down my list for the house).

The siding does unfortunately need to be pulled up, but 75% of it can go right back (the other 25% is on order). I was hoping to not have to do it, but it's not sealed very well and was the likely source of some rodent problems the previous owners had, no easy fixes there. 10%-20% of the floor insulation, and over 50% of the ducting insulation has rodent pulling type damage. I'm just going to put in plywood and Tyvek to about 33" up from the sill. The rest of the house has some kind of silver backed builder board about 1/8" thick, almost no plywood outside of the flooring anywhere in the house. Going to have to use thin plywood, or maybe a substitute to minimize bulging on the siding. Good to know I don't have to insulate that wall.

Thanks for the advice on the bracing too. That's pretty much what I was thinking. The center beam needs A LOT of bracing, hardly any longitudinal, and none lateral currently, not really tied in to the wall. I'm thinking about anchor bolts too... but that's off the insulation topic.

Thanks again!!!!!
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Old 08-05-2015, 09:51 PM   #6
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Increase the insulation (R-4) on the ducting to today's minimum, at least (r-7) I think... with vapor barrier. The silver 1/4" sheathing is structural sheathing, acceptable for shear walls then and today- ThermoPly; https://www.google.com/search?q=ther...utf-8&oe=utf-8 In mid 70's we used to throw nails at it for bulls-eye points during lunch breaks... lol. Used that stuff for quite a while, cheap substitute for plywood (before OSB sheathing). Used that as sheathing if house had wood lap siding, used T1-11 otherwise, very popular. Add some strapping to the bottom sides of the post to stay on footing during "the big one"... aluminum to recycle is good money..... just start a new thread for each topic, lots of good people here.

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Old 08-06-2015, 07:44 AM   #7
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Interesting. Seems like Pacific NW is one of the few areas that does seem to be a better candidate for vented crawlspaces.

http://www.djc.com/blogs/BuildingGreen/?p=383

Note: In the link above, they supplied mechanical ventilation to the crawlspace to lessen the amount of communication between the home and the crawlspace air.

Seems like the cost benefit side of the equation leans more toward unvented crawls in the Pacific NW, if only slightly.

The ventilation must be adequate in these cases and it appears that recommendations are toward the 1:150 NFA.

There may be more vents in the space, but you appear to have what looks like two 8" by 16" vents. Assuming there is no screening or any other cover in them (unlikely unless you want squatters in there), you have about 1.8 square feet of NFA. That mean that crawlspace should be no bigger than 270 square feet. It looks a wee bit bigger than that, but I don't know the size from the picture or the total venting equation.

See the recommendations for the venting section: http://www.homeenergy.org/show/article/id/776/viewFull/

Note they recommend R-30 to R-38 in the floor. Like Gary said above, the vapor control layer is facing the wrong direction.

Questions:
  1. What is the flooring above the crawlspace?
  2. Do you have adequate storage in the home and would this space ever be a good conditioned storage area?
  3. Do you know what the radon levels are?
We rarely see crawlspaces that are that friendly to work in as what you have there. While the cost benefit might lean toward vented if you aren't putting anything down there, we tend to have our clients want/need more storage. I can't stand attic storage so a good and relatively tall crawlspace like this is a find.



While the expense of the conditioned crawl might be more as a result of the materials you will need to use (foams vs. batting), I would argue that making that work as a sealed unit might be easier. Maybe not, however, if you see yourself using it for storage, I would seriously consider the sealed route.



Be sure to check your venting calculations as listed above.



Thanks Gary...I keep learning.
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Old 08-06-2015, 10:33 PM   #8
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Me too, everyday! ken, make sure to check very own WA State amendments to the IRC Energy Code and Building Codes. Couple on energy; http://www.wabo.org/assets/pdfs/ener..._checklist.pdf

More detailed;http://www.energy.wsu.edu/Documents/...s%20Energy.pdf

Gary
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Old 08-06-2015, 11:05 PM   #9
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That is some serious specifics. Some of their window stuff is way off in terms of their projections on efficiency but that is comprehensive to say the least.

Looks like they call for R-30 in the floors.
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Old 08-08-2015, 07:39 PM   #10
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Thanks guys

sorry I hadn't responded didn't get a e-mail this time for some reason. I just measured the height it's 4'2" to the bottom of the joist +/- a few inches. the house is 1900 square feet, the crawlspace is less than half that. I was going to do the siding first but the weather got in the way, just got done ripping out the floor insulation an hour ago. 3" R11, faced on the top, bottom and long sides. It's in 13-14 55 gal bags now. The joists are 2x10 so there was a 4" to 6" gap to the sub-floor. No rodent droppings before demo, about 1,000 now. Lots of construction debris up there too, looks like they replaced the sub-floor under the sink and DW. I'll probably have to replace the ground vapor barrier after the demo on the vent insulation (was hoping to do that last).

Can't wait to get some additional structure in there, the joists are the only thing stabilizing the center beam possibly only through friction.

There are currently 5 vents at roughly 6" x 14" I will be adding some more and looking through those links, but first...sleep.
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