We are getting into green rehabs and doing them under LEED for Homes. We'd like to add insulation to the basement walls without having to drywall. As a Habitat for Humanity affiliate, we don't have any room for additional costs so adding any more finished space is cost prohibitive.

Anyone have any ideas to attack this? Any cool products I may not be aware of?

Any foam insulations on the interior need to have a half-hour thermal barrier over them (half-inch gypsum is typically the cheapest).

But in basements controlling groundwater vapor flows without foam makes mold control difficult. Basement insulations MUST allow drying toward the interior, but putting studwalls & fiber insulation next to the foundation all but guarantees a mold problem.

The best/cheapest would be insulating the exterior with EPS with parging over above grade portions. But if it's already backfilled and the siding is up it's tough to retrofit- cheaper to bite the bullet on a worthy interior system, but it won't be free:

See: http://www.buildingscience.com/documents/reports/rr-0202-basement-insulation-systems

Unfaced iso-board or unfaced 1lb EPS (marketed as roofing insulation) held in place with furring strips through-screwed to the foundation & taped/foam-sealed at the seams goes up quickly without the expense/complication of a studwall. The thermal barrier (half inch gypsum, or OSB if the foundation is well drained on the exterior) can be mounted directly to the furring strips. It doesn't have to be finished space, just legal from a code POV. (I did my own basement this way with unfaced R20 iso recycled from a factory roof.)

Under "cheap stuff you might not have heard about", you may be able to get away with a stucco-sprayed non-structural "bead crete":

http://www.builditsolar.com/Projects/SpaceHeating/BeadFoamCrete.htm

It would take a 4.5-5" layer to amount to get it up to R8. It should be breathable enough, but from a fire-code POV I'm not sure if that too wouldn't need a thermal barrier, since its 90% EPS by volume. (I'm considering using it as crawlspace-floor insulation over a poly vapor barrier, which would have a lower thermal barrier requirement, if any.)

I'd think bead-crete should qualify for some LEED points as a recycled material, but it may be difficult to categorize.

Recycled XPS, ISO, and EPS is available from a company called InsulationDepot and probably other places as well. They'll sell in small quantities FOB their Framingham MA facility if you can pick up, but they won't ship below a certain volume. If you're doing a multi-home development it might be worth a tractor-trailer load delivery, since it's usually ~1/3 of the new-goods pricing for some pretty-good stuff. (Mostly recycled from roof demolition of large flat-roofed buildings.) That should also improve your LEED score.

Google  INSOFAST or look at other post's

We've used intumescent paint in the past. Depends on the local officials.

Look at Quad-Locks Retro-Fit system with the drywall and get an R-18

Do you mean this system?

Good ideas but I'm seeing lots of dollar signs. Remember, the key is "low cost". We're a Habitat for Humanity affiliate and can't afford most of these propietary "systems".

Habitat,

I'm with Insulation Depot, Dana1 mentioned us in his post. We do sell 100% recycled/reclaimed insulation boards, and do so at 50% - 70% less then new insulation. We have 50+ warehouses throughout the country to serve our customers. Why don't you give me a call and I'll be happy to investigate whether we can be of any help to you. You can reach me @ 888 820-2760. Good luck, and please call with any questions.

 

Regards,

David Volpe

Do you have anything that is fire rated so we can insulate without putting up drywall? That is ideal since we have free DOW rigid board but it can't be exposed thanks to fire codes.

I've worked with Habitat in the past on LEED projects, and have run into the same free foam issues. See if you can get Dow to provide Thermax for your job: http://building.dow.com/na/en/products/insulation/thermaxsheathing.htm


In many jurisdictions, it meets ignition barrier requirements with no drywall, but check with your local code official to see if it meets their requirements.

Habitat,

I can't do any better then free Dow insulation.

I ordered Thermax to wrap the footings of my ICF walls last year. Ran into some sort of availability problem, but don't remember the specifics. I think it was something to the effect DOW quit distributing it west of the Mississippi, or something of the sort. Anyway I ended with most of the insulation being R-Max, which is basically the same but doesn't have quite the same ESR report. The thermal rating of Thermax, IIRC, is better than R-Max. I taped all the joints with aluminum HVAC tape. Anyway, in the end the BI bought off on it. I sure wasn't going to stir things up any more with him than I needed to!! My crawl space is my HVAC supply plenum so I had to comply with a more stringent thermal requirement than applies to unoccupied crawl space.

Using foil-faced sheet goods for basement insulation can have unintended consequences due to it's very high vapor retardency- it's a class-I vapor retarder (times 2!). Insulating down to the frost line or the full upper-half is usually OK, but insulating all the way to the floor results in higher moisture levels in the foundation wall that can lead to high moisture levels in the foundation sill (possible rot hazard), and efflorescence & spalling on the above grade portion of the foundation. (Spalling and efflorescence damage can be mitigated with a layer of sacrificial parging, but it takes a perfect sill-gasket to keep the damp out of the wood.) With unfaced or fiber-faced EPS/XPS/ISO or up to ~2" of 2lb foam (all class-III vapor retardency or higher) some amount of inward-drying capacity is retained, the moisture content of the foundation wall is lower, which lowers the risk.

In very-cold climates (8-9000HDD and up) the risk is pretty low anyway, (Canadian building codes even require interior-side vapor retarders in basements) but in climates under 7000HDD the risk is real, and class-I vapor retarders like foils are best avoided.

Still, just an upper-half treatment is at least 75% as good as a full-wall treatment, since the above grade portion itself usually accounts for more than half the heat loss, and the lower 1/3 is typically near the average sub-soil temp year round- well over the heating-season average for the above-grade portion in most areas. Heat loss through the wall near the floor per sq. ft. is similar to the heat loss through an uninsulated slab, measurable, but not a deal-breaker in conventional housing the way it might be in a net-zero building.