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Buffalo A · Mar 29, 2009, 05:51 PM

I am planning on finishing my attic with a tray like ceiling (4' knee walls and 4' wide flat ceiling that will have about 8' of 45 degree slope span towards the knee walls). I have seen so many different versions of proper ventilation from "baffles with rolled insulation, to foam insulation, and gable vents with solar powered vents." My attic will have about 10' tall ceilings, and get's about as cold as 30 degrees in the winter and 90 degrees hot in the summer. What would you recommend for proper ventilation prior putting up dryway / knee walls?:confused:

21boat · Mar 29, 2009, 07:14 PM

The 'baffles" from the over hangs should already be there to insulate the existing ceiling below the attic. The other place you need baffles is where the Knee wall contacts existing roof truss to let air flow pass through there to the upper peak to vent.

Do you have a ridge vent and or gable vents?

If you don't have a ridge vent I would put one in. When you do the finish area you will block gable vents if that's what you have. The ridge vents will vent the (tray) are well and pull directly from the soffit vents which for a finish attic is also a must.

In simple terms ALL needs to vent well. The better the venting the less chance of trapped moisture and mold or losing (R) value.

Another thing I see here is the statement it doesn't get that cold. The insulation in the finish attic is more along the thought of HEAT getting into that finished attic. So heats the enemy here not the cold. I would still use (R 30) because of the heat transfer into the new living space.

Foam is not the what to go here. Fiberglass with vapor barrier facing the warm side of the wall/living space.

Here is the ratio for roof venting and a guide on other related roof issues

http://inspectapedia.com/interiors/atticcond10.htm

Buffalo A · Mar 30, 2009, 07:19 AM

21 Boat: I do not have gable vents in the walls, just a few soffit vents on the over hang. Regarding ridge vent, I assume a ridge vent goes along the joint where the truss peaks, and allows airflow at the peak of the roof? Is that something I would need to install from the roof top? At least 40' high to get on the roof. I would like to take some pics for you, this is great! Thanks for your help!

21boat · Mar 30, 2009, 08:17 AM

Ridge vents are a must hear to get as much Hot air out as possible, especially since there are no gable vents.

If you install a new ridge vent and I always talk the customer into venting the whole ridge.
1. It's the max that can be vented and helps draw air up from the soffit more.
2. doing the whole roof ridge and stopping it about 1.5 feet from the ends helps give the roof a cleaner line to look at. I don't care for a roofs that's partially vented in looks. The vent looks more like a protrusion than it being part of the roof.

Just on a side note you can't over vent. The roof is there only to protect the insulation from rain/ leaves/ big winds/and animals. Its not there to insulate the house. Insulation is for that.

Can you add more soffit vents to get the air flow ratio you should have?
If that's a problem then Gable vents should be put in to help the air flow.

The perfect scenario is full ridge vent and full gable vents.

Buffalo A · Mar 30, 2009, 10:16 AM

Can you install a ridge vent over an existing roof (estimated 15 years). Or, would you recommend a new roof with new ridge vent as well?

21boat · Mar 30, 2009, 06:32 PM

No you can install a ridge vent any time It's a little more work but we do it all the time. Is the roof rough? You can get a square or so of shingle if need be to cover the flange and of course you will need some for the top of the ridge vent for looks
It's a bit rough and ruins a saw blade basically.. Just lay out ridge vent saw cut the asphalt and the peak on each side for air to come through. Slip ridge vent under the last layer of shingle and the other course over that, There are many different ridge vents follow those instructions. I would guess when Ridge vents first came out there was probably more put on old roofs then new at one point.

Buffalo A · Apr 1, 2009, 11:16 AM

21boat: Thanks again for your help here. I had a contractor (1 of 2) come over yesterday and give me an estimate on a roof. Clearly, there is still some life in the roof, although, he did suggest I might want to re-shingle the valleys. There are at least 3 layers on the gable roof, so it would require a tear-off etc. Quick estimate: 28 square (roughly $15,000). As a general contractor, he also pointed out some priority issues before roofing / attic. I have a rotted post on my front porch that should be replaced due to poor drainage. Even worse, he explained my foundation should be worked on first. My house is 90 years old, and sits on a rock foundation (roughly 24" deep). I have no clue when it was last worked on, but the mortar is cracking and turning into sand causing some of the rocks to become loose and bow in certain areas. Anyway, he is going to work up an estimate on that repair which requires inside and outside and excavation, etc. It sounds like a moderate DIY job if I had a solid week or so. Do you know or suggest anything as to proper technique for repair of the foundation? The contractor explained it to me yesterday, but I was taken back because he was there for my roof. Sounds like I would need to remove all the loose particles, and then re-mortar with a special bonding agent? Also, can seal if need be. Not sure what he meant about the grade level?

21boat · Apr 1, 2009, 03:12 PM

Lucky for you I live in an area where many houses here are in the late 1700s up. The mortar in your foundation is not like today's mortar and should be matched. The reason is that foundation needs to breath and if moisture comes through and hits newer harder it blows out the old beside it.

The mortar mix you see used by brick layers today contains two ingredients: lime and Portland cement. In fact, the Portland cement ratio is quite high. Old brick layers used to mix their own mortar on the site by blending lime with Portland cement. Old houses, say over 100 years, rarely had any Portland cement in the mortar. The bricklayers just used lime and sand.

This is what you need to use for the foundation.

LIME MORTAR, LIME PUTTY, MASON FURNISHES TECHNICAL NOTES

I'm A G.C. in restoration and rehabs need to know the old ways to do proper repair and mixing new with old.

Grade level is just that. There's rough grade and finish grade.

logan176 · Apr 4, 2009, 05:37 AM

Personally, if you're finishing off attic space and turning it into living space I'd go with spray foam. I had heating and cooling issues with the upstairs rooms in my Cape. After spray foaming with Icynene there are no more problems. My rooms are warmer than all my surrounding neighbors. I have no problems with ice dams (I don't even have icicles) and snow stays on my roof MUCH longer than my neighbors' because the foam keeps the heat in better.