Unfinished basement, Cgi 5 gas boiler, Z vent. The outside air is making the basement cold. Can it be louvered?
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Hi all,
So Ive just finished sealing the rim joist with 2″ XPS (Dow Blue board) and spray foam, sealed the perimeter between the walls and floor with silicone, installed a air tight sump lid but was still getting drafts.
So Ive tracked it back to the Z vent for our CGi5 boiler, it seems the air is coming in through the z vent and back that way. It has the Z Vent termination cap on outside but was wondering if it could use a metal louver on the outside so when the boiler isnt firing it the drafts stay outside?
Im asking because Im uncertain about the gas, the Cgi has no pilot just a pizzo igniter to start it when the thermostat or water tank needs it, so just need to see if its possible or am I going to gas my family?
We will one day finish the basement, and I was planning to seal that room off and add a outside fresh air vent anyway as its currently taking the combustion air from the basement itself, I was hoping to keep the basement warmish with it and the fridge thats down there.
Im in NY about 20 miles NW of NYC
Any suggestions would be great
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Replies
Don't modify what the manufacturer has your installer install. And make sure no snow builds up around the exhaust. It should be well out of any possble snow levels.
Close off the room but do so to code. The needs of gas fired units need to followed.
The builder put it in, I wasnt sure if it was meant to leak air like that or if something hadnt been installed in the Z Vent like a one way value or something.
Darren,
First, some clarifications.
Your reference to a CGi boiler, I assume, refers to an atmospherically vented gas-fired boiler manufactured by Weil-McLain.
Your reference to Z-vent, I assume, refers to the vent pipe used to vent the combustion gases from your boiler to the exterior.
If I'm understanding correctly, then I agree with AJ. Don't modify the exterior termination in any way.
Darren,
Leave the vent alone ! These boilers require that vent to be unobstructed . My advice would be to construct a mechanical area separating the CAZ from the living space , floor to deck , with an intake vent for combustion air .
Thanks thats why I knew to ask the experts (You guys) :)
Richard, that was the plan EVENTUALLY so Ill have to do it sooner than later I suppose if I want the rest of the basement to be warm
So would I use 2" XPS with 5/8 drywall to finish the room? Is that to code or would I need a fire rated drywall in its place?
Code and Code enforcement varies by location...
Unsure which wall you are talking about using xps on, but foundation wall - with 2"(R-10) covered in Sheetrock for fire protection would be a little light...but it is "unconditioned" sort of....worth insulating/covering if it's a combustion space?
The isolation/partition wall would need sheet rock on each side if using xps (overkill on insulation costs IMO)
Darren,
Build that wall as if it were an exterior air tight wall with the exterior being the mechanical area . In the meantime get yourself some metal tape and tape all the Z vent joints tight as you can , that should lessen the draft . Are you sure it is a draft , do you feel it in other areas or just when near the boiler area ?
Richard
Have some Nashua foil tape, taped the seams, they look like they have used fire resistant caulk (red firestop Im assuming when they have put it together)
So I for shits and giggles put a small box over the vent outside then came back inside to see if the vent is the issue, and it isnt so Im totally at a loss as to what it can be, the rim joists are all sealed, the sill plate has a gasket, the sill plate I spray foamed when I did the rim joist, the only other penetration is the sump pump output but the sump pump cover is airproof so Im totally lost as to what it can be
As the air movement/draft it only seems to be around the boiler (moving cobwebs) and I dont see it anywhere else (the odd spider now is marooned after I did the recent rimjoist/sill plate insulation)
Anyway thanks for the advice, will have to build a wall now to close off the draft and add an external air intake
Regards
Darren
...you sure it isn't just convection due to a hot boiler?
a smoke pen (or inscense) or something might also help pinpoint it.
Perhaps not germane to the question but it certainly is to the planet: If you don't absolutely need XPS, and I can't think of any reason for that need, don't use it. I wouldn't have brought it up since it's already done but I don't think you should even consider using it for the remainder of that room. My understanding is that it has orders of magnitude more global warming potential than other foams. This is because of the blowing agents used. You do much, much more damage to the atmosphere by using it than you could possibly ameliorate by the reduction of petroleum products for heating by using XPS for increasing air tightness and insulation.
I think it's really important to not get so caught up in the trees that you don't see the forest. Sorry if this comes off as shrill. Don't mean it that way!
Used an incense stick but was inconclusive, the boiler was cold so not that all external penetrations are sealed
Have to pull all the fiberglass batts to figure if there is a hole somewhere (living room is upstairs so there isnt but cant figure what else it can be.
The hunt continues
Regarding the wall insulation, 20 miles NW of NYC is the warm edge of US climate zone 5. To hit IRC 2012 code min for zone 5 requires R15 continuous insulation, or R19 in a framed wall (the latter of which is riskier, due to the moisture susceptibility of the cold edge of the framing) :
http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_11_sec002.htm
To hit that performance one COULD use 1" polyiso trapped to the wall with a batt-insulated studwall, or go with just 2.5-3" of polyiso held in place with furring through-screwed to the foundation, which would have a much lower impact than XPS due to the comparatively benign blowing agent used. XPS is only about 5x more damaging than EPS, maybe 6-7x more damaging than polyiso per unit-R, but it really IS more damaging. That's not "orders of magnitude more" damaging, even though the blowing agents used are almost two orders of magnitude more damaging per lb (but not per unit-R for the finished product). That's really "only" about one order of magnitude more damaging per R per square foot after factoring in the embodied emissions from making the polymer itself, not looking exclusively at the blowing agents. But even 5x is a pretty big uptick in damage.
And by the time it's been in service for 50 years slowly outgassing the damaging HFC blowing agents, it's performance falls to about the same as EPS of the same density.
Better yet, instead of using virgin stock foam, try to find a source for used goods, for which the environmental hit has already been taken. With used good you are just extending the service life, reaping more benefit from the environmental hit already taken. Reclaimed/used foam, comes as a huge 60-75% discount below virgin-stock retail too. One way to find local sources of reclaimed, surplus or factory-seconds goods is to search your local craigslist materials section for foam insulation or rigid insulation:
http://newyork.craigslist.org/search/maa?query=foam++insulation
http://newyork.craigslist.org/search/maa?query=rigid++insulation
Dana, I had been thinking about blowing agent for XPS being 2 orders of magnitude more damaging per lb. Still, I think 5x worse per R per square (cubic?) foot is bad. There's no reason to accept a 500% worse global warming potential with XPS than other foam boards. But I like used foam board of all kinds too.
Yes Ive been buying only seconds, the XPS I got from a guy (Celtic Building Materials I think) in Yonkers, $20 a 2" 4x8 sheet Dow Blue board off CL
When I get to finish the basement in total I have been speaking with 2 guys on CL re Polyiso in New Haven CT the other Kingston NY both are sort of the same distance from me, so 46 sheets later will need a rental truck to get it all, but as I said Ill get there when the money is there.
My goal at the moment is to slow the stack effect as much as I can and to keep the first floor floor as warm as possible, there is R11/19 in the basement roof (open) thats why I used the XPS blocks to fill & seal the rim joist (with spray foam for the edges) to try and keep the basement as warm as possible with a boiler and a fridge
Eric- we're on the same page. I just wanted to point out that 5x is still substantially different from 100x. (More than an order of magnitude less.) I'm always pushing folks to design closed cell polyurethane and XPS out in favor of EPS, polyiso or rigid rock wool whenever it's easy to do so (and it's dead-easy in basement insulation applications.)
Apparently Darren got the memo too, given that he is only using reclaimed goods.