Post of a house where the Roofer greatly increased the stack effect 2/16/18
Turbine Exhaust Roof Vents
There are certain situations where turbine exhaust roof vents are the only viable option. These are when your house has very limited intake vents and you need to utilize Nebraska’s wind to force air up through the attic and out the peak. For most roof designs however, a turbine exhaust roof vent is a poor choice. If the wind isn’t blowing and your intake air is inadequate from not having enough intake vents or having the vents partially clogged, then snow easily sucks in through these vents and piles up on your insulation, melts, and causes stains in your drywall ceiling below. Rain can suck in as well. A general rule of thumb when selecting your vents or trying to correct your existing home is that the intake air must equal the exhaust air. The picture above shows a roof with too many turbine vents. This causes snow & rain to suck in through the top and also leads to excessive loss of conditioned air. In the winter, you’ll literally be sucking heat up out of your home when the winds blowing. In the summer, your air conditioned air is being sucked right up out also. Every time the wind blows, these vents create a significant stack effect on your home which can raise radon levels. That suction can overtake radon mitigation fans causing the radon levels to rise above 4.0 pCi/L. Homeowners that think their family is safe from radon may not actually be.
What is the Real Reason Turbine Exhaust Roof Vents are Installed?
Roofing Contractors love to up-sell these vents when replacing your roof and it has nothing to do with making an improvement on your home or trying to increase your home’s energy efficiency. They make a nice profit of $200+ per vent when they only cost around $30-$40 a piece. It pads an extra $1,000 or more to their roofing job.
What Damage is Caused by Installing The Turbine Vents on Your House?
When a Roofing Contractor installs these vents on your roof, they are cutting a round hole larger than a basketball through your roof deck. If you decide to remove them and switch over to a continuous ridge vent system, those holes are so large that the only way to properly repair them is to remove those sections of your roof deck, install new plywood or OSB decking, install new underlayment, and re-shingle over the new decking. There is no patch you can install over these large holes that makes it safe to walk on afterwards. This conversion over to a better continuous ridge vent system or turtle vents costs enough money for a licensed Roofing Contractor, that the homeowner will be a little irked.
What Risks Are There If You Leave Those Vents On Your Roof?
1. Roof Leaks – Almost every one of these turbine or whirly vents we see on our Home Inspections has signs of leaks in the attic insulation directly below them. Some leaks are bad enough that they cause water damage stains in the ceilings below.
2. Higher Utility Bills – In the Omaha area, our housing stock does not have plastic across our ceilings separating the attic from our living space or every opening sealed with spray foam. Adding these turbine vents increases the stack effect on windy days. Being we are in Nebraska where it’s windy most of the time, the conditioned air is being sucked up and out to some extent.
3. Increased Radon Levels – Building Science proves that wind forces on a house can increase the stack effect…which is the upward pressure inside your home. The greater the stack effect, the higher your radon levels can potentially be. With these vents, the higher the wind is blowing, the greater the stack effect if you don’t have an attic space sealed off from your living space in your house.