Damper for make up air vent... yes or no

[4Kings]

A job transfer has taken my wife and I from Missouri to Northern Michigan earlier in the year. We bought a new house that's 10 years old and according to the realtor and inspector is very well built and tight.

There are two make up air vents in the house, one is routed directly into the return air system and the other just dumps into the basement. With the recent cold spell I have noticed that a lot of cold air is being dumped into the basement. Since we have plans to finish this space in the near future, I'm concerned about the amount of cold air that seems to be flowing into the space.

I do have natural gas for both the furnace and water, and I understand the need for this make up air supply but is there any reason not to put a damper on the vent pipe and if so, any recommendations as to which type.

 

[rlitman]

The make up air to the basement should only be supplying as much air as goes up the flue, and can be routed to the boiler room, so it shouldn't have much effect on the finished space. What sort of furnace and water heater venting do you have?

The make up air into the return plenum can be routed through a heat recovery ventilator for some savings. Or you can possibly just seal that up.

 

[4Kings]

Both the furnace and water heater have fan-assisted vents that run horizontally to the backside of the house through pvc pipe.

 

[mustangacman]

You could get an April Aire power damper that you could wire into the system that would only open when system is operating. They sell them in 4" up tp 12" I think it is.

 

[yeldogt]

You will need to evaluate what is actually required. If the water heater and furnace are two pipe they don't need makeup air. All houses require air change and w/ the ability to tighten up a structure -- we now have homes where the inside air can become unhealthy.

I'm a spray foam user -- so my houses are tight. I'm also in a radon area .. so the desire for a positive pressure house is also ideal. I typically have a large intake 8-10 inches that "Y" off to twin dampers. One side is controlled by the stove/range hood the other is a separate controller fitted to my whole house dehumidifier for fresh air exchange. The controller allows for general air makeup and has an override should more people be around. My last house has a 4" bleed pipe to my VS HVAC -- it's always on.

A large intake w/o control just dumping into the furnace will most likely be too much... uncontrolled basement dumping for appliance will also be too much. Ideally -- a blower door test is done on the house to determine leakage -- many houses leak and in the heating season have so many holes that they pull lots of air through the basement vent because of the stack effect.

Typically trying to control the heat loss from the stove/range hood is not worth the trouble -- they do make electric kits that preheat the air allowing the intake air to be distributed anyplace. I stick mine far away in the HVAC return and never really notice much change -- it still goes through the dehumidifier. The damper on the intake matched the range hood pipe. Bathroom exhaust is direct and short duration -- so, I don't worry about it.

You need to figure out how the NG appliances work and go from there.

Many use an ERV or HRV for general make up air -- another possible solution. While the better ones are nice as they can dial in a positive pressure -- I find the other way works and allows me to use the dehumidifier. With the new HVAC VS equipment --- things are changing -- that equipment is always running and can in some locations negate the need for the dehumidifier.

Even a fully sprayed house w/ excellent windows will leak -- some around me use 60cfm uncontrolled bleed intakes to introducing fresh air and pressurize the house. It all determined by a blower door test. Some states have free energy audits.