Insulated crawlspace cost??

kaiser715

kaiser715

Doing hard time
Joined
Jun 1, 2006
Location
7, Pocket, NC
Talked with builder about the quotes he is getting back from his subs.

Our new place is going to be 3000sf on one level. I want to do sealed/conditioned crawlspace.

Insulation contractor is coming back $6000+ higher on the sealed and insulated crawl, vs. open crawl with a VB on the ground. Is there really THAT much more $$ in sealing and foamboarding the walls, vs. properly putting VB on the ground (seems that would be the same with either method) and insulating between the joists?
 
There is zero return on investment of foam board or spray foam on crawlspace walls.

Depending on the house, yes foam board/spray foam on the walls is more than fiberglass in the floor.

I like spray foam on the band of the house, from the sill to the subfloor.

To generalize greatly, it would cost around $1/sq ft for us to do vapor barrier, dehumidifier, and fan, to get the crawlspace to pass the minimum code for CO, as a closed crawlspace.

Then it's just a comparison of cost Between insulating the walls vs the floor to get the co.

My data comes from temperature samples from identical crawlspaces on 3 houses each with different insulation. 1 was 2" spray foam, another was 2" polyiso board, the third was fiberglass in the floor.

All three had identical vapor barriers, and no foundation vents, dehumidifier, exhaust fan, and gasket & polyiso on crawlspace door.

All 3 temps were within 2 degrees of one another 68-70, while exterior temp was 17 degrees and snowing...


If I can help at all pm/text/call me.

I'm in a crawlspace everyday, and convert about 150/ year to closed crawlspaces.

Not trying to pimp my services, just stating my experience with the topic.

I can't tell you price on spray foam or board on the walls, as it's now rare that we do them.

Pm or ask @moldman05, he should know those #s.
 
kaiser715 said:
Talked with builder about the quotes he is getting back from his subs.

Our new place is going to be 3000sf on one level. I want to do sealed/conditioned crawlspace.

Insulation contractor is coming back $6000+ higher on the sealed and insulated crawl, vs. open crawl with a VB on the ground. Is there really THAT much more $$ in sealing and foamboarding the walls, vs. properly putting VB on the ground (seems that would be the same with either method) and insulating between the joists?
Click to expand...

It's 2017. Do a sealed crawlspace. You might need a different contractor to do it if the difference quoted is $6k on new construction.
 
Fabrik8 said:
It's 2017. Do a sealed crawlspace. You might need a different contractor to do it if the difference quoted is $6k on new construction.
Click to expand...

We're in Lee County...about a generation behind.

Most common response we hear from builders: "we've always done it this way...."

Sealed crawlspace is foreign to some of the builders. HVAC guy said "I've heard about it". Don't even ask about geothermal..., etc

Sent from my SM-G930V using Tapatalk
 
Mac5005 said:
There is zero return on investment of foam board or spray foam on crawlspace walls.

<snip>

My data comes from temperature samples from identical crawlspaces on 3 houses each with different insulation. 1 was 2" spray foam, another was 2" polyiso board, the third was fiberglass in the floor.
Click to expand...

I'd love to nitpick the methodology here, but you're right - when I've messed with adding insulation at the slab edge/under slab or in a foundation wall, it doesn't do jack for the energy model. If there's occupied space in the basement, I could see the insulation contributing to general thermal comfort, but the ROI there is nill.

kaiser715 said:
Don't even ask about geothermal...
Click to expand...

Don't waste your money ;)
 
If I may bend this thread a little, & ask Mac5005 a question? I just had a premium garage door installed with 2" foam insulation. In doing so, I learned that attached attic space, nor 2 walls, are insulated. I feel like if it was all insulated, the unheated/cooled garage would stay a more constant temp. Warmer in the winter, & cooler in the summer. I doubt it will have any effect on the house itself. Is it worth having the walls & attic pumped?
 
shawn said:
Don't waste your money ;)
Click to expand...

That's about what I have figured out, but still interesting tech. I wish the local HVAC guys would at least have enough knowledge of it to say I don't like it because _____. What do you see as the bad about geothermal? Cost to install, time to payback, mechanical issues, etc?

The house will be right on a deep 3/4 surface acre pond.
 
No payback if you're drilling wells. Dunno about the pond.
 
rodney eppes said:
If I may bend this thread a little, & ask Mac5005 a question? I just had a premium garage door installed with 2" foam insulation. In doing so, I learned that attached attic space, nor 2 walls, are insulated. I feel like if it was all insulated, the unheated/cooled garage would stay a more constant temp. Warmer in the winter, & cooler in the summer. I doubt it will have any effect on the house itself. Is it worth having the walls & attic pumped?
Click to expand...


I'm sleepy and hard for me to think through this one completely, quickly.

Insulated the most where the greatest temperature differential is.

If that is greatest from ceiling to attic, or inside vs outside of wall.

Stopping air infiltration is the greatest concern.

Are you conditioning the garage?
 
shawn said:
I'd love to nitpick the methodology here, but you're right - when I've messed with adding insulation at the slab edge/under slab or in a foundation wall, it doesn't do jack for the energy model. If there's occupied space in the basement, I could see the insulation contributing to general thermal comfort, but the ROI there is nill.



Don't waste your money ;)
Click to expand...


I agree completely, but I can't argue with the results.

Some assumptions were taken, but crawlspace temp/outside temps were all taken same time/date without disturbing crawlspace.

All were similar sq footage, height, and age. Assume thermostats were set close to each other.

No argument here, but no substantial change in temp to have proof of concept of potential energy savings despite drastic cost difference.

The data from princeville/advanced energy also backs this up.


As far as builders not knowing, we "air quality control" ( my dad @moldman05 and I) have been converting crawlspaces to closed type since 1999 before hurricane Floyd, and the houses studied in princeville, post Floyd '99.

The NC building code didn't allow new construction of closed/conditioned crawlspaces until the changes in 07.

We do existing and new houses from Roanoke rapids to Wilmington, to Fayetteville, Atlantic beach, Kinston, Goldsboro, Greenville, rocky mount, And raleigh.

I wouldn't build a new house unless the builder was at minimum familiar with energy star qualification requirements that include a closed crawlspace.

Whether you pay for the energy star qualification or not, that's the minimum I would shoot for.
 
Yeah 6k sounds really high for new construction, we paid around 5k and had a full mold remediation done too. Our house is about half the size of yours, but with full access to the crawl there should be a significant labor savings.
As for ROI, I wouldn't say it's the best, but for us the mold problem was what we were worried about. Now our crawl is nice and clean and our floors stay warm in the winter. Cooling cost dropped in the summer, heat in the winter didn't significantly change. I'm planning on blowing in more insulation in the attic and replacing some windows.


Also, having the insulation on the walls makes it so much easier if you have to go under to run wires or whatever.
 
RobMcBee said:
replacing some windows
Click to expand...

Winner, winner, chicken dinner.

Windows are expensive. But a good, air-tight window makes a big difference. If the window is catching a lot of sunlight, low-e coatings will make a big difference in the summer, too.

@Mac5005 - Any recommendations on a dehumidifier? We have a couple of the stupid, old-school portables down there. I need to plumb them to drain, and they're a bit noisy, but otherwise "fine". That's a big piece of the puzzle that gets overlooked (and honestly, that I used to not think was particularly important). From what I've seen, the hard-mounted units are a bit pricey, but it that comes with better controls, better reliability, or less noise, that might be worth it to some folks.
 
Mac5005 said:
I'm sleepy and hard for me to think through this one completely, quickly.

Insulated the most where the greatest temperature differential is.

If that is greatest from ceiling to attic, or inside vs outside of wall.

Stopping air infiltration is the greatest concern.

Are you conditioning the garage?
Click to expand...
NO. Thanks
 
shawn said:
Winner, winner, chicken dinner.

Windows are expensive. But a good, air-tight window makes a big difference. If the window is catching a lot of sunlight, low-e coatings will make a big difference in the summer, too.

@Mac5005 - Any recommendations on a dehumidifier? We have a couple of the stupid, old-school portables down there. I need to plumb them to drain, and they're a bit noisy, but otherwise "fine". That's a big piece of the puzzle that gets overlooked (and honestly, that I used to not think was particularly important). From what I've seen, the hard-mounted units are a bit pricey, but it that comes with better controls, better reliability, or less noise, that might be worth it to some folks.
Click to expand...


I put some seal n peel on the ones in the living room and that alone made a huge difference. A few in the front have been replaced but are still kinda old. Front of house gets all the afternoon sun. They are on my list....
 
shawn said:
Winner, winner, chicken dinner.

Windows are expensive. But a good, air-tight window makes a big difference. If the window is catching a lot of sunlight, low-e coatings will make a big difference in the summer, too.

@Mac5005 - Any recommendations on a dehumidifier? We have a couple of the stupid, old-school portables down there. I need to plumb them to drain, and they're a bit noisy, but otherwise "fine". That's a big piece of the puzzle that gets overlooked (and honestly, that I used to not think was particularly important). From what I've seen, the hard-mounted units are a bit pricey, but it that comes with better controls, better reliability, or less noise, that might be worth it to some folks.
Click to expand...

If under 3500 sq feet and one large crawlspace, and not chopped up with additions,

A single 65-70 pint dehu is all that's necessary if the walls were air sealed correctly.

I recommend keystone units as an entry level unit based on price, reliability, and warranty. Should be around $200. Has the correct air flow for crawlspace use, and the permanent drain connection is high on the unit, making gravity draining without a pump much easier.

Use some 1.5" ID rubber or flex pvc tubing cut 1.5" long pushed over the wheels to make it stationary.

If you plan to be there for 5-10 years and can afford it, Honeywell has a USA made unit that is top of the line. We sell/install about 60 year of these.

The online prices are just nearly the same as my price, but I get contractor support when/of one fails.

Stay away from aprilaire/Santa fe. These are energy hogs and are extremely noisy compared to the honeywell.

The aprilaire won't drain properly without ducting attached, and if you try to damper the air to get the drain to work, it gets even louder.

Stay away from units that move the air in/out the top.

I always gravity drain and try to avoid using a condensate pump if all possible as it's another piece of equipment prone to fail.

Obviously if the space is chopped up, or larger, use multiple dehu.

If smaller sq footage, you can drop back to smaller capacity, but that may not change price on Dehu much.
 
I wound up putting a dehumidifier in our crawl when we had all that rain but the temps were to low for the ac. Bought a $300 unit that was on sale for 225. It's a 70 pint with a drain. I set it on 55% and it's done it's job. I wish I had seen what @Mac5005 had said about the top output. I used some sheet metal I had and made a small duct for it. Worked out great because now it sucks in from one side and I made it blow out the other.....

We'll see how it does this summer
 
To the op,

Do a sealed crawlspace with dehumidifier.

Do whichever crawlspace insulation is cheapest.

Area of floor x fiberglass price vs crawlspace wall perimeter area x board or foam price.

Generally it takes a lot square footage and a short crawlspace wall for fiberglass price to equal price of spray or board foam.

Take that money and upgrade windows or insulation elsewhere.

Or add another row of block/brick to make crawlspace 8" taller.

I despise fiberglass but the only thing I like about it, it's cheap and meets the minimum.

Fiberglass loses 36% of r value when you raise moisture content in it by 1.5%!!!!!!
 
R-19 batts under floor .50 a sq ft. 2" foam board on crawl space walls $2.25. R-10 spray foam on walls $3.25 sq ft. 6 mil ground vapor to meet code , covering all soil, fastened, seams overlapped a foot, .35 a square foot. 3 ply 12 mil, everything wrapped, seams taped, $1.30 a sq ft. Dehumidifiers $200 to $1200
 
@shawn @Mac5005

Met with contractor today, and he gave me copies of the quotes from the insulation contractor.

House plans are set at 3000sq ft, one level. Brick exterior.

Walls and attic:
R38 Unfaced batt
24" cardboard baffles
Exterior walls R-15 unfaced batt
Fireplace chase rear R-15 unfaced batt
Behind tubs R-15 unfaced batt
Interior walls (baths, laundry, master) R-13 Kraft batt
Window & door foam
Bottom plate caulk
Top plate sill seal
Walls and attic cost....$4471.00

Option 1 - vented crawl space (which I don't want)
R-19 unfaced batt
17" support wires
Poly on crawl (6 mil poly)
Crawl space cost (vented option)....$1734.00

Option 2 - closed crawl
Temporary poly on crawl 4 mil ($344 of total)
2" rigid foil board on foundation walls
10mil poly on foundation walls
(foam and wall poly $2591 of total)
12mil poly on crawl floor
band joist R19 unfaced batt
(floor poly and band joist batts $2503 of total)
Crawl space cost (closed option)....$5438.00

Total insulation package for vented crawl is $6,205
Total insulation quote for closed crawl is $9,909


Comments?
 
You should do r19 batts in floor, $1500

6 mil poly vapor barrier on ground and up the wall. $1050

And honeywell dr65, $1000

Install a small bathroom fan that vents from crawlspace to exterior, to put crawlspace under negative pressure.

anything beyond that is a waste of $$ and materials.

Use the cost savings from doing 6mil poly and r19 batts to pay for the honeywell Dehu.

The poly should go down last when everyone is done with crawlspace and house is ready for CO, so it won't get trashed by others.

6 mil is plenty. Overlap the seams a foot, and glue it to the walls.

Use two layers at crawlspace door.

Build with no vents to seal, solid fill with sand for any concrete slabs for porches.

1/2" polyiso insulation and gasket on crawlspace door.
 
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