Replies

1. 
   zolton | Oct 15, 2010 02:32pm | #1

   Furnace fresh air vents

   Janet,

   Are you sure you were asked to cut "fresh air" vents into the mechanical room door? Usually, combustion air for fuel-burning appliances is required to come from outside the house, via a make-up air duct. That's usually a six inch metal pipe drilled through the rim joist, terminating inside the mechanical room.

   Door vents like you describe were required long ago. But in order to prevent backdrafting of appliances the code changed some years back and now combustion air is mandated to come from outside.

   This issue has to do with the large amount of air that is required by a furnace, for instance, to properly combust gas or oil. As we strive to make houses more airtight, the potential rises for there not to be sufficient air available for combustion purposes - air that used to leak freely in around doors and windows, and through cracks between the foundation wall and framing materials.

   In a case of there not being enough make-up air available, the operating appliance can draw combustion gasses backwards down fluepipes. Those gasses contain carbon monoxide, among other toxic items. So this is a serious health issue. It not only can affect air quality, in severe cases it can be (and has been in the past), fatal.

   So, adding "fresh air" vents to the mechanical room door might be an attempt to provide more combustion air to the appliances within that room; there is more air available in the rest of the house than there is just in that one room. However, I'd check with your local building department to see if you're required to add an exterior fresh air intake. That would be the safest bet.

   If you do install an exterior make-up air duct you wouldn't necessarily need (or want) vents in the mech room door. In fact, it would probably be better to keep that room sealed up as well as possible. The fresh air intake from outside allows cold air in, and if it finds a way out of that room it can cool your basement. Plus, a nearly-airtight mechanical room makes for a quieter environment in the nearby living spaces...

   Sorry for the lecture. I know it's not what you asked.  Zolton

2. 
   PSeverin | Oct 15, 2010 06:14pm | #2

   Install proper make up air for the furnace.

   I'd like to second the previous response.  Even in older leaky houses,  with dryers, kitchen range exhaust and bathroom exhaust going you can quickly run out of fresh air to expel.  So talk to the furnace man about installing a vent to the outside.  

   Sometimes the vent is routed directly into the return air duct.  Or the duct comes into the room and terminate a certain number of inches above the floor.  In Minnesota people  occasionally place a bucket under the fresh hose to create a trap for cold air flowing constantly down on the floor.  Check with you local building official.  They will probably tell you you don't have to do anything, (they only can enforce something that you are improving) but that you would be smart to do it.   You might also check with a realtor to see if it is one of the things asked for when a house is checked out before a sale.  If you ignore this make sure there is a carbon monoxide detector near by.

   None of which is an answer to your question.  I've always considered pine to be relatively forgiving.  Oak is where I get tear out and that lovely leopard wood is impossible.

   Peter