Venting a roof is, historically, standard practice. There are two ways to do it:
1. Vent the roof from eave to ridge by use of eave vents and ridge vents. These can be a simple as holes/ opening at the eaves that allow air to flow upward toward the peak and then up and out under the ridge cap.
- At the peak of the house there will be something- tiles, shingles, a metal cap- that top off the roofing and block water from flowing in.
- This is often 'lifted' with a ridge vent that allows the air to flow out.
- This method requires unobstructed air flow from eave to ridge.
If you have this kind of venting and you want to insulate the roof itself, you would need to put up some baffles before you insulated between the roof rafters so that the air could continue to flow in each rafter bay from eave to ridge.
It is a good idea to use some sort of pre-manufactured product or screening at the eaves to prevent critters from coming in with the air.
2. Install gable vents. If you plan to insulate the floor of your attic only, then gable vents are a good answer. They are simple grilles that go at each end of your attic that allow air flow through the attic space. These also often include some sort of screen to keep bugs and critters out.
Where to insulate?
The big question is - if you want to really insulate your house and make it more efficient - should you insulate the roof itself or should you insulate the floor of the attic?
- The floor of the attic is easier, however often in bungalows you 'live' in the attic - meaning that there really is no attic space, the roof is simply the ceiling of the second floor.
- Or you may have cathedral ceilings from the first floor. So you cannot insulate the floor of the attic.
Also, you may have a lot of duct work in the attic space, in which case I always recommend insulating the roof itself.
- This creates a continuous envelope of conditioned space that the ducts are within.
- This prevents heat loss (and cool loss) from the ducts themselves which is something you get if ducts are passing through un-insulated attic space.
Insulating the roof itself
If you are going to insulate the roof itself you have 2 options:
- Insulate with any insulation product other than closed cell foam and install the eave to ridge venting I described above.
- Install closed cell foam insulation right up against the underside of the roof sheathing and negate the need for a vent. This is often the easiest answer if you do not have a lot of room for insulation.
Closed cell foam insulation is very efficient and it acts as somewhat of a vapor barrier.It is a bit more expensive but it may be your most cost effective option to get a good exterior envelope in the end- depending on your exact situation.
Contact an insulation contractor
Your best bet is to call a good insulation company that is savvy about foam insulations and energy savings.
- They will be able to analyze your situation and tell you the best insulation options.
- They will also be able to see the roof you have on and modify their recommendation based on the type of roofing you have. (Not all roofings act the same with all insulations. )
And regarding hard wood floors: often the most green thing you can do is use locally prevalent materials.
- In Maine you would probably do the most sustainable thing by using a locally harvested, FSC (Forest Stewardship Council) Certified product - like pine.
- You could also get bamboo or cork - both highly sustainable - but they often cost a good deal more because they are 'popular'.
- They often also ship from a long way away so your overall carbon footprint is probably least when buying from your local FSC mill.
For more information:
Read "How effective are the different attic ventilation methods? I read mixed reviews, and many have a commercial bias." a Q&A answered by Danny Kelly.