A year ago, I bought a house that needs a new roof. It’s a small cape with a gambrel roof, and was built in 1850 (in New England). The roof currently has 4 static vents (two on each side). I’ve gotten two estimates, one is with static vents and one is with a ridge vent. I’m trying to decide what to do. I’ve been doing research on the net, and I plan to get back to the contractors and ask them some questions. In the meantime, I thought some of you might have ideas or opinions about this.
I’m not concerned about the aesthetics. I assume the pitch of the roof is adequate for a ridge vent. One of the contractors mentioned that there’s a beam between the top and side of the roof (which I now know is called a purlin). I don’t know how he knew that, or if he just assumed it, or whether it makes any difference to the vents at the top of the roof.
So which vent is the best for this situation? And why?
I am an instrumentation engineer, not mechanical, but I would think that if they have been venting for 250 years, that’s the way to go.
What is your house wiring like?
The wiring is ok. I don’t know how to describe it but it’s not ancient, and I have had an electrician in and he didn’t complain about it.
The main thing is ventilation, which means air flow to keep moisture (and rot) out. That normally means both soffit and ridge vents.
The earliest method ran bare wire inside the wall, supported with nails or screws. I’ve never spoken with anyone who had to deal with that. I’m curious how a house is wired after construction is complete.
Sorry for the digression
There are soffit vents, but as the one contractor mentioned that there may be a beam between the gables (a.k.a purlin), I don’t know what they’re doing. But my question is about the upper part of the roof.
Static (or roof) vents and ridge vents both accomplish the same thing. Sounds like roof vents are perhaps the better option. Or maybe I’m not understanding the question.
If there is not a significant difference in cost and it doesn’t require some significant modification to the roof structure the ridge vent will provide better and more continuous ventilation. One of the problems with box vents is they aren’t placed high enough on the roof and you get a pocket where moist air can collect if you don’t have regular airflow, but if you have adequate total vent area and the vents are well distributed this shouldn’t be a big problem. The presence of purlins shouldn’t have any real impact on which type you select unless they somehow interfere with where the box vents need to be placed.
Soffit vents are primarily to promote airflow in the eaves where moist air can collect, and as @Chefguy says these should be in any new construction (and are generally easy to retrofit onto older construction). If your house doesn’t have soffit vents and you are replacing the roof anyway it is probably a good time to just have them installed. It’s a small expense to make the house more livable and robust, especially in a rainy climate.
Stranger
There would be a lot of details involved in installing an effective ridge vent in an old structure like that. The simple concept used most often goes hand in hand with modern stick construction, and usually premade trusses holding up roofs. your house might be built with a ridge beam that the roofing boards are secured directly to and cannot operate as a ridge vent. You may not have simple eaves that can be vented and would need gable venting to provide fresh air. Personally I would want s thermostatically controlled gable exhaust fan that would remove moisture from the attic and help cool the structure in summer. But there would be a lot of details to consider. I think the best approach in your case would be looking for similar structures in your area and what they’ve done for ventilation.
Ridge vents are almost worthless without continuous soffit venting (that was not typical in older homes). Unless there are insulation sheilds tacked to the underside of the roof sheathing that allows soffit intake air to reach the ridge, without insulation blocking its path, I think you are better off leaving the gable vents in place.
Followup: I talked to the roofer about ridge vents, and he says that Owens Corning requires ridge vents in order to quality for their 50-year warranty. He was very reassuring about ridge vs static, so I’m going with ridge.
I would be immediately wary of someone making that proposal and find a different contractor. The ridge vent they install may be worthless, and other terms of the warranty may make you ineligible anyway. At least talk to another contractor first.
Could you clarify the difference between ‘ridge’ and ‘static’ vents that you are considering. The term ‘static’ vent is somewhat ambiguous. A ridge vent does not work by itself either,.
Types of roof vents. Ridge with baffle vs static.
So you are planning on using a fan as well? Do you already have one? I assume it’s post and beam construction with a ridge beam. You mentioned purlins which indicates roofing boards running from the ridge to the eave. Do they plan on cutting those boards for the ridge vents?
It has soffit vents. The quote says will install eave vents “as needed.”
Are you just getting the roof re-shingled or is there insulation involved also? I can understand the warranty would be based on a properly vented attic that doesn’t overheat or collect moisture. The use of passive ridge and soffit/eave vents has been heavily promoted throughout the building industry since the 70s despite reports that it hasn’t as efficient as originally believed. In short, moisture is bad for attics. It’s bad for the building materials which are mostly exposed in the interior, it’s bad for insulation which is most needed in attics, and it’s going to be bad for roofing in multiple ways such as overheating and allowing snow and ice build-up. The reason it doesn’t always work well is that rooves aren’t all constructed the same way and don’t always create the air circulation needed to keep attic spaces cool and dry. For instance, purlins are beams parallel to the ridge beam between the ridge and eave. There are usually more than one. Purlins can interfere with the air circulation that ideally would have cool air entering from the eaves and passing between rafters or trusses without interference. What I’ve been able to find out on that problem is that ridge and eave vents may be insufficiently sized, but additional gable and box vents may prevent air from the eaves ever entering.
Anyhoo, I’ll go back to saying look for other 175 year old houses in your area to see what has worked for them. Whatever has been done on your house for almost 2 centuries has worked so far, so I would be careful about cutting into any part of the structure. Does this contractor have experience with old homes? Maybe he’s just the guy to use, I don’t know, but I went through all this with a house half the age of yours.
So is the floor of the attic insulated? Any other insulation up there? And what kind of venting is there now?
As I understood, part of that venting pushed since the 70’s - from soffits to ridge or high-up vents - included a moisture barrier (usually of plastic) between the insulation and the interior. Otherwise, warm moist air will seep through cracks and such in winter and create wet/ice spots in the attic. I imagine a very old house does not have that protection.