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Big 10-18-2005 08:22 AM

Insulating difficult 2nd floor design
 
We have a 2 story cape in Long Island. The unique aspect regarding insulating the attic is the design of the second floor.

1) The triangular roof sits directly onto the cinder block frame with no eaves or soffits.
2) The 2nd floor is "hexagonal tube" inside this triangular roof. Floor is about 12 feet wide and the other 5 surfaces are about 4 feet each (imagine a pentagon with its top flat). The angled interior surface follows the roof deck line on the rafters.

(I tried to make an illustration, but formatting would not work!)

3) The 2 "triangular tubes" that run along the bottom are used for storage, accessible by 3x3 bifold doors. The triangular tube on top is not accessible at all.

4) There are gable vents on each end, an attic fan and another roof top vent of sorts. ( I can't access where they enter the attic top - only view them from outside).

Insulation Questions:
A) Since we regularly access the attic space for storage, It seems that I should insulate the rafters (against the roof deck) and the joist space above our 1st floor living area. Correct? My question is that since there is not a soffit, how is the insulation properly applied on rafters?
B) The joists rise 5.5" above the ceiling board, that does not seem to be enough clearance for the proper R value insulation. (there are boards along the joists to accomodate storage that limits the height of insulation)
C) There is only 5.5" of clearance for that 4' where the angled-wall line runs along the the roof deck line. Therefore, I can't access that "triangular tube" space that is the interior roof peak on top of ceiling - I can't lay/blow insulation in that area. Additionally, if I install insulation batts along each of those rafter spaces I will be plugging that space and cutting off any possible airflow.
D) Becasue there are no soffits, but there are gable vents and a fan vent, I assume that I do not have proper circulation and the air only moves at top triangular space. Any fix for this?

Thanks to everyone that made to the bottom of the page! I decided I better give a chance to answer before going into anymore detail!

Thanks

K2eoj 10-18-2005 10:11 AM

I grew up in one of those houses and know the layout. I would avoid trying to insulate the 2x6 rafters. You could end up with a condensation problem. I would try to isolate your storage from your attic, (upper most space), at least for the winter, and try to make your storage area into a dead air space, (no moving air). Dead air is the best insulator and is what all insulation products try to achieve. If I had to add insulation to the uppermost area I would cut some new roof vent and while the holes were open , would blow some insulation in, and then complete the roof vents. I personally don't think adding insulate to the upper area would do much for you. I would also keep an eye out for condensate after any changes were made. In my experience in my area, condensation varies with the people living in the house and with solar orientation. <P>
You'll probably get some different opinions here and that is the way it should be. HS

Big 10-18-2005 10:30 AM

Yes, your idea makes the most sense. The 2nd floor was always humid in the summer due to the fact that the previous owners applied the batts against the roof deck.

I removed all the insulation and blown in celluose (original 1947 work it looks like!) because they let their cats in there and the area smelled terrible in the summer from "left-over" cat "stuff".

They also had a roof leak, which they repaired and reshingled - but cut off the 1st floor bathroom vent pipe so it was exposed to the attic area. I assume the original roof vent for that is what caused the leak and they just shingled over it to stop it.

I think I will take your suggestion and just insulate the attic joists and attic side vertical walls- leaving the rafters exposed. HOWEVER, that leaves that entire 4 foot slanted section along the entire 2nd floor (on both sides) within 5" of the roof deck. Should I try to stuff batts in between those rafters to insulate the living space? It seems as if that would stop the circulation of the triangular side space up to the top triangular space - the only place with vents (no soffits or eaves here).

Teetorbilt 10-18-2005 10:41 AM

Right now I'm more interested in that vent pipe. Which vent is it, plumbing or ventilation?

Big 10-18-2005 10:58 AM

I am not an expert, but the engineer said it was plumbing pipe vent from 1st floor bathroom. used to go thru roof, but they cut it off so it vents into the attic.

K2eoj 10-18-2005 11:16 AM

Big, that's bad! Call a plumber.

Big 10-18-2005 11:27 AM

Can't I just add an extension on the pipe and put it through the roof deck and seal the the vent correctly? Or a professional plumber should do the work?

mighty anvil 10-18-2005 01:00 PM

Extend the vent pipe through the roof without a plumber but it might be smart to use a roofer if you have any other roof work for him. Roofers are cheap insurance not only against future leaks but potential paralysis or death so I suggest you take it.

IMHO your only option is to insulate the roof with professionally applied spray-on foam, or rigid foam boards cut to fit. This would require refinishing the walls and ceiling but "the absence of alternatives clears the mind marvelously" (Hank Kissenger). It would also allow increasing the depth of the rafter space which provides a good payback in heating cost. Roof venting should not be required. Don't worry about shingle life it won't be affected even though the manufacturer's warranty will be voided (and they would claim inadequate venting no matter what you did).

K2eoj 10-18-2005 03:47 PM

[
Quote:

quote=Big]Can't I just add an extension on the pipe and put it through the roof deck and seal the the vent correctly? Or a professional plumber should do the work?
[/QUOTE]

You can extend it yourself. Be careful. If the city is snaking the sewer lines there could easily back up enough methane gas to light. (Ask me how I know that). I always try to make roof penetrations near the ridge. Everything is less likely to leak near the ridge. I agree with MA on using a roofer which would not be critical in my area because it never rains anymore. HS

plumguy 10-18-2005 11:13 PM

Quote:

Originally Posted by Big
Can't I just add an extension on the pipe and put it through the roof deck and seal the the vent correctly? Or a professional plumber should do the work?

Around here a vent thru the roof must be 18"-24" above. You definately need to address this problem immediately!!! Sewer gases are toxic and pose a serious threat to you and your'e family!!

Big 10-19-2005 09:26 AM

Question for own knowledge: What exactly does this plumbing vent pipe connect to in the first floor bathroom? How does this venting process work?

plumguy 10-19-2005 10:06 AM

Quote:

Originally Posted by Big
Question for own knowledge: What exactly does this plumbing vent pipe connect to in the first floor bathroom? How does this venting process work?

All plumbing systems and fixtures need to be properly vented in order for their water seal (trap) to be protected and for proper drainage. The venting system allows air to enter the system. There are many ways a trap can lose it's seal and the most popular would be thru siphonage. The vent system also allows the sewer gases to exit you're system thru the roof and into the atmosphere. That is why it is critical that you solve you're issue. Also, depending on where you live some areas allow air admittance valves, which means you would not have to penetrate the roof. You could install this valve also known as a mechanical vent right on top of you're pipe.

Big 10-19-2005 10:47 AM

That's an interesting alternative! So the device could be placed on top of my exposed pipe in the attic to resolve the issue. Great idea.

this link describes your suggestion too:

http://www.toolbase.org/techinv/tech...chnologyID=140

plumguy 10-19-2005 12:19 PM

Quote:

Originally Posted by Big
That's an interesting alternative! So the device could be placed on top of my exposed pipe in the attic to resolve the issue. Great idea.

this link describes your suggestion too:

http://www.toolbase.org/techinv/tech...chnologyID=140

That is the animal! Around here they are illegal and can only be used with special permission from the state board. The valve would be clamped,glued,etc to the top of you're existing pipe depending on you're application.

K2eoj 10-19-2005 03:08 PM

It's non-complying in my area too but i would get one on there as soon as possible.


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