OGStilts

Problem: every winter these people get these WATER leaks around several doors and windows.

I show up to look at it and there is icicles 2'-3' long around the entire house so immediately I start thinking attic ventalation and attic insulation problems. The house is about 80 years old with an addition put on about 10 years ago so the attic was split up into two areas.

Old attic area: As we enter the attic area I notice that the air temperature feels like it's about 60 degrees (meanwhile it is 24 degrees outside). It has the original floor boards and is being used as an storage area. Where floor boards are broken or missing you can see that someone has made a half-hearted attempt at blowing in insulation but there are many areas where it's very thin or completly missing to the point where I can see the wall plates below. There are no vent baffles in this area but there is a ridge vent. So I figure this area just needs to maybe pull up some of the floor boards so we can make sure to get a healthy dose of blown in insulation everywhere (2x10 cavities) and need to add some vent baffles and make sure they are unobstructed.

New attic area: It's a completely seperate attic area with it's own access point. Again as we enter, the air temperature is comfortable probably around 55 degrees. There is an attic furnace which was NOT put in a seperate insulated furnace room as called for by local code. The insulation in this area is R30 unfaced and it doesn't look like there is any kind of vapor barrier on the warm side of the insulation (either side for that matter). This area does have vent baffles in every rafter cavity and has a ridge vent but when you walk around the outside of the house there is only a 12" x 12" soffit vent about every 7' to 10'. Since the insulation in this area seems to be relatively sufficient, I'm thinking that this area is so warm because of the lack of soffit venting and from the heat that the furnace is giving off. Now I'd really like to just build some walls and ceiling around the furnace, insulate them and call it a day with that but the furnace location (and the way the duct work is run) makes it much more difficult if not impossible to do without moving the unit and it's ducting. I was wondering can I run vent baffles the entire length of the rafters from the soffits to the ridge and just insulate this entire attic area similar to what you would do in a cathedral ceiling area? This would basically turn this entire attic area into a furnace room without needing to move the HVAC equipment, gas line, water line (humidifier), duct work, etc. I seem to remember a debate about this practice going on a few years ago but I'm not sure if that was here or over at JLC or what the final conclusion of that discussion was. I'd also replace the current soffit venting with continuous soffit venting around the entire house.

Sorry this message is so long. This problem and solutions seem relatively obvious to me so I just don't understand how this homeowner has had so many different contractors look at this over the past couple of years and claim they can't find the problem. I guess that is making me second guess myself.

Thanks.

WXdan

Hi OGStilts,

Sounds like you have an challenge on your hands! I feel that the most important thing to bear in mind is that a cozy house equals air flow management plus insulation.

Without controlling the air flowing from or into conditioned spaces, the insulation loses it's effectiveness. So yeah, you can certainly ventilate the attic as much as you want: however, the occupants might react by cranking up that furnace to replace all the heat they are now losing outside resulting in a continued hot ceiling which is most likely causing your ice dams.

This is what I would do:
1. Blower door test the house to establish flow in cubic feet per minute at 50 pascals (CFM50) and compare it to your building tightness limit (BTL). Reference: Residential Energy by John Krigger or hire someone to do it.
2. During the test investigate air leaks and air migration from the conditioned space to the unconditioned space. (There is a whole methodology of how to do this). It flows in some unexpected ways.
3. Air seal (duct work, wall cavities, balloon framed walls, chimmney perforations, and T+G amongst all the other ways that air travels)
4. Test again to make sure that you did what you hoped to do (lowered the CFM50 to the BTL)
5. Insulate.

Re: attic venting. Most code is for a net area of vent per floor area (i.e. 1 square foot of venting per 150 square feet of attic floor or something). If you get the air sealing down, that is all that you should need.


Cheers,
-Dan

OGStilts

I'm not sure if we are talking about the same type of leaks. Sorry original post said "leaks" but I've revised it now to say "water leaks".

Basically the ice damns are creating sitting water on the roof and it's working it's way into the house. I had my guys out there all day today removing snow and melting ice to stop the leaks but now I want to make sure I solve the cause of the ice damn problem.

My biggest concern is how to create a seperate furnace room out of the mess I've got. I may just get stuck having to move the furnace and rearranging the duct work. Would like to avoid this if possible.

Maybe what you are suggesting is that I will learn more about my insulation problems then I currently know by doing the blower test. That could be valuable. I've never had a blower test done before on any any house but have seen it on video and read about it briefly. I'm going to educate myself more on this practice and how it may apply in this case. Thanks for your advice.

RayGoerdt

the blower test will indicate what kind of air loss there is from a poor vapor barrier, but not how much insulation is needed or is present.

Try to determine if the problem is air transfer (vapor barrier) or heat transfer (insulation) often it is both.

Most air leaks will show in the unheated (attic) areas as frost build up or blackening of insulation/framing. Most heat loss areas will show as melted areas of snow on the roof, possibly creating ice dams.

OGStilts

Thanks Ray,

Yep, there is no frost or any sign of any moisture damage inside the attic just a lot of snow melt on the roof creating the ice damns.

No comments yet from anyone saying whether it is a bad idea to make the attic with the furnace in it a conditioned space or not?

tom m

Sounds like a good option....I see no problem with it. If I understand what your saying it sounds like you a a forced air horizontal furnace and the plenums are radiating heat into the space. So either go with your idea or change the ducts with insulated board maybe even wrap them.

OGStilts

Thanks Tom, I'm going forward with it. I don't see the downside of doing it this way.

maceycon

I don't run baffles up to the ridge for cathedral ceilings and don't think it is a good idea. You can not get enough insulation in the rafter bay with the baffle unless you could use extra wide rafters and then you have condensation issues. I like to get the cathedral ceiling R value up to 50 without vents. I think you could do the same thing here. If the furnace is heating the attic space enough to melt the snow. I would go with a warm roof system and solve that problem. I use to get to an r50 with rigid insulation strips but now you can have it sprayed in depending on the thickness of your rafters.