Would better venting mean higher heating cost?


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Old 01-31-06, 12:40 PM
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Would better venting mean higher heating cost?

I did my roofing last summer and improved ventilation while I was at it. In years past, I got a lot of icicles, and that problem has gone away. However, it seems my natural gas usage has gone up considerably. Was I gaining something of an insulating effect from my less-than-adequate attic ventilation?

I don't doubt that I can benefit from working on better insulation, I just was curious if my theory is valid.
 
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Old 01-31-06, 01:02 PM
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Yes. There are two ways of getting rid of ice dams and icicles - improving ventilation and adding insulation, so you're half done.
 
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Old 01-31-06, 03:06 PM
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Yep, right on all counts. Snow melting on the roof is a sure sign that you need more insulation in the attic. Either that or it's a sure sign spring is near.
 
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Old 01-31-06, 06:46 PM
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Your theory is valid

It is pretty common to find that inadequate ventilation was keeping in some heat. Bring your insulation values to the levels recommended for your area, make sure that the new insulation does not obstruct your airflow, and you should have lower energy consumption, and no roof melting or attic condensation.
 
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Old 02-01-06, 08:39 AM
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i asked b4..

but i kinda cant find it. I have vaulted ceilings through out house. Roof is probably made of 2x6 or 2x8. I live in michigan. What is the best way to keep ventilation and get some type of insulation. My gas bill is crazy.

p.s. sorry to kinda hop on your post
 
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Old 02-01-06, 10:17 AM
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Vaulted Ceilings

For your situation, in our area we would recommend a second roof deck. If possible, the insulation would go under the original deck, and the new deck will be 4-5 inches higher than the old deck with vertical air channels conducting heat from the eaves to the ridge vents. The end result is effective, but this is a very expensive way of doing it. We've done it four times in the past two years, and the people were VERY intent on fixing their problems. But for most normal mortals, laying out that kind of money just doesn't cut it. So, as always, it depends on what's important to you.
 
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Old 02-02-06, 09:34 AM
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Talking ok...

so is there another option than laying out another roof deck??? If not, how do you go about doing it??? Just piggyback 2x6 on existing roof joists?? Do I need to get someone to figure out if my existing roof can support the weight?? Thanks
 
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Old 02-02-06, 10:49 AM
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How to...

There may be other choices, but to get both ventilation AND insulation when you have limited roof space to work with usually means going to the outside. It is always a good idea to have an engineer look at the existing situation. We had one case where this was being considered and the structural engineer said don't even think about it until the central supports are reinforced (they were not well built and were barely keeping the house standing). When this method is OK, you'd usually need a building permit, since you will be changing the structure of the house. We've put 2x6 on end over the existing rafters and laid the new decking on top of that. In one case, we couldn't go under the existing roof to add insulation, so we ended up putting the blue rigid insulation on top of the old deck (2 inches of insulation and 3 1/2 inches of ventilation space). You also will need to build new soffit boxes at the eaves and provision for ridge vents at the top. It's a lot better to have these details built into the house, and very expensive to retrofit after.
 
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Old 02-03-06, 03:13 AM
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Talking ok...

thanks for the info. Didnt realize the heating/cooling troubles when I bought the house, but got a great deal, in a great city, in a great neighborhood so there are not really to many complaints. I appreciate your help. Just one more question. Do you pull up the existing sheeting on the roof or dont you??
And can you blow in insulation to the lower part in you dont pull up the sheeting?? Thanks again. :glocke:
 
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Old 02-03-06, 05:50 AM
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How to...

Access to the attic depends on the slope of the roof. Lower slopes make it difficult to work from inside the attic, and sometimes the only way is to remove the sheathing from the hard-to-access spots, do the work, and reinstall the sheathing.

If one is going to install a second deck, I would leave the original decking in place. In the situations I described earlier, we stripped all the roofs down to the deck and built the new spacers and deck over the old deck. A couple of times, we completely redecked the roof, but because the ventilation could be taken care of from inside the attic, it wasn't necessary to build a second deck. In those cases, we had to be very careful NOT to shift the rafters, since they often do not have any spacers or blocking keeping them in the right position.

The challenge with much of the roofing work is that the roof is part of a system, and you cannot blightly change one part of the system without affecting something else. The roofing system also interacts with the house, so any major changes need to look at all the possible aspects. Too often, someone tries to correct a specific problem (say, ice-damming), and the solution creates new and more serious problems.
 
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Old 02-03-06, 11:36 AM
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ok...

sounds good. I have a number of a guy in my area from these forums. I will talk to him in the spring to see what we can do. Also, I have NO ATTIC, my roof has plaster on one side and sheeting/roof shingles on the other. Probably a 2x6 or 2x8. Thanks for all the info;
 
 

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