Proper Roof Ventilation Requirements
Over the course of my career, I have been to thousands of houses giving estimates talking to home owners, have been in hundreds of attics trying to troubleshoot the issues that homeowners face with their roofs, and I have come across one common roof problem, that many (homeowners and roofers) seem to think that just adding a vent will solve the problem. In some cases, (newer homes built to today’s current building code) they are right. Other cases on the other hand (houses built prior to 1980) there is a 50/50 chance they are wrong.
Prior to the 1980’s, they didn’t have stuff such as “vented soffits” which you see on all houses today. Back then, and earlier than that, they used wood soffit, which unfortunately blocked the air intake which you need for proper air exchange. Because these were not of a big concern back then, homeowners decided to install aluminum vented soffits over top of the wood soffits that already existed without even drilling holes to allow the air to get in. So when you’re walking through a neighbourhood and you notice someone has a brand new roof, they have the required roof vents, yet they still suffer from Ice Damming, this is most likely the reason as it is the most common.
Now, there are other issues that may affect the performance of your roof. I will go over a check list for you to refer to before you hire a roofing contractor. A proper ventilating roof must meet these criteria.
- Soffits must be well-ventilated; air circulation in soffits must be unobstructed. This basically means the same as I have mentioned above. Checking to make sure that you do not have wood soffit underneath the aluminum soffit that will not allow air to flow through. This does not mean you need all new soffit. You can fix this issue by removing the bottom row of plywood and cutting holes into the wood to allow air to flow through without disturbing your soffits. This can be done cheap, and effectively when your roof is being done. Another thing to check, is to make sure the insulation is not pushed up against the underside of the roof deck. This will prevent the air from flowing from the soffit to the vent. This can also be remedied when the holes are being cut into the soffits. Your roofer can install “Baffles” at the same time. Below is picture of how this would work.
We had removed the bottom row of plywood, installed the baffles, and are about to cut the holes. I chose these two pictures so you can see how the old plywood soffit is blocking the air from getting in. Took our crew a total of 45 minutes to do all this work. The holes were cut with a 4 inch wood auger bit.
Here is another example
Above are three pictures of a home, where the homeowner has not yet installed aluminum vented soffits. You can clearly see how your attic would not be venting properly as there is no air intake for this house. Now, to do new soffit and fascia on this house probably would have cost around $4500.00, and for some, that’s out of their budget, and that’s understandable. Not everyone is walking around with $4500.00 hidden in their sock. This solution above, meets your ventilation needs for 1/8 the cost of new soffit and fascia. It’s functional, cost effective, looks good and gets you a properly vented attic space.
- Attic insulation in Canada, should have a minimum rating of an R-30. This translates to 13 to 16 inches of blown insulation. This will provide enough insulation to prevent heat loss from your ceilings causing the snow to melt on your roof. Over time, improper attic ventilation could lead to “Insulation Compression” causing a lower “R” value for your attic. Insulation Compression is caused by the humidity lost from your ceiling, building up in the attic. When there is not a proper working vent system, the humidity gets trapped in the attic and starts to compress the insulation. As a result; compressed insulation = lower “R” Value.
- Access door to the attic should be well-insulated. I have been in plenty attics, and can tell you, there are plenty access hatches out there that are under-insulated. An easy way to remedy this, is to go to your local Home Depot. Buy some 6 inch Rigid Foam Insulation and a tube of PL Construction Glue (rough cost $30.00). Cut the insulation 1/8 inch smaller than the hatch, and glue it to the back side of access hatch. Voila, fixed.
- Air evacuation ducts should not discharge into the attic, or within 3 feet of the soffits. One of the most common mistakes I have seen, is bathroom vents, dryer vents, range hood vents etc… venting through the soffits, or just venting into the attic. This is a improper as the main vents on your roof will actually pull the warm air from your Air Evacuation Duct back into the attic, where in the winter will condense on your rafters, and on the bottom side or your roof deck, eventually leading to mould, or plywood de-lamination. Venting these ducts directly into your attic, will clearly do the same. Air Evacuation ducts should be connected to insulated flex pipe and sealed directly to the ceiling fan and a CT-4 or CT-6 Vent. The type of vent depends on the CFM output of your fan. This way the warm air has no choice but to be pushed outside, well away from your soffits.
- You should never mix a “Static Ventilator” with a “Passive Ventilator”. Few people recognize the difference between a passive ventilator and a static ventilator. A static ventilator allows air exchange, where as a passive ventilator allows for evaporation. Passive ventilators would be low profile vents like ridge vents, mushroom vents, gable vents or even a gooseneck ventilator for flat roofs. They do not allow for air exchange but merely let the air evaporate out through them. The air enters through the soffits into the attic, then gradually escaping out through the ventilator. A Static Ventilator would be turbine ventilators and Maximum Ventilators, or even Venmar Ventilators. All three can replace the attic air, and they function with the combination of wind and pressure differential, creating a chimney effect, replacing the attic air. When you mix these two together, the static ventilator will create its chimney effect, trying to pull air from its closest source. This in all cases, should be the soffits, but when you have passive vents installed in the same attic space, the static vents will actually pull air through the passive vents, resulting in a poorly vented roof. Basically, only the top three or four feet of your roof are being vented, instead of the whole roof, as it should. This will result in hotter attic temperatures in the summer, poor air exchange in the winter, leading to all the problems we just went over in this blog. All from one mistake.
This is why you should consider Wright Brothers Roofing for your roofing needs. People hire Wright Brothers Roofing not because they are looking for someone to slap a roof together, they hire us because we are problem solvers and we have the knowledge of how things work.