OK you weekend warriors.

I just did a energy audit in a home near my house. Owner wanted to find more ways in which he could make his home "tighter" in an effort to save money.
Part of the BPI inspection protocol is to do what is called a CAZ test or evaluation. This is a Combustion Area Zone inspection. This CAZ test is to determine if the furnace, boiler, hot water heater is getting enough fresh air for combustion. Part of this test is that we set up a worse case environment to see how the draft works on the heating system and hot water heater.
In most homes there is enough natural air leakage into the area in which to supply the heating systems and allow for the draft air to go up the chimney.
But with the big push to seal up and save programs it is quite common to find conditions where the flue gasses are NOT going up the chimney and are spilling into the home. Oftentimes being pulled into the heating return duct or AC duct system and delivered to the house as deadly CO gasses.
In any case I did this evaluation and found that most of his flue gasses were going into the house every time the furnace fan operated. Which results in a failure of this test.
Of course the issue is resolved by upgrading to a power vented hot water heater, but had I not checked this as part of the audit, this homeowner could have gotten quite sick or even died as a result.
What my point is, is that whenever you decide to seal up and save, you must think about more then just preventing that air from leaking out, but understand that you still need air leaking in. Remember any work done to a home effects the rest of the house as well. So even sealing your attic can have undesired results somewhere else.
Remember years ago when we began sealing our attics in the 70's OK most of you may not have, But us older then dirt folks do. We used plastic to cover over the vents in an effort to keep in the heat in the winter. And some would remember to take it down in summer to let out heat. Many did not, and the result was damaging mold because of trapped moisture. Well we all learned that was not such a great idea. Same goes with what many people are doing today, by sealing up their homes.
Some of the best intentions can backfire if your not careful. So when your climbing around in the attic this weekend and putting down all sorts of insulation or doing air sealing in the rest of the home that I always suggest on many of my posts. Remember there is equipment elsewhere in the home that may suffer from the result of you trying to do the right thing.
You can do your own mini CAZ test on your own. Turn on all the fans in the house. Close all the windows. Turn on the blower on the furnace and turn on the dryer as well. Then taking a mirror turn on your hot water heater and wait about on minute. Then place the mirror next to the draft hood and look for steaming to occur on the mirror glass. Or you can simply put your hand next to it but be careful not to burn yourself on the hot pipe. Do you see a fog on the glass or excessive heat coming out when the hot water heater has been running for a short while? If so you have a home that just may be too tight to be safe.
I have seen basements so tight that the door at the top of the stairs slams shut when the furnace is operated. This oftentimes results in burnt fronts on the hot water heater, or burnt cabinets on the front of the furnaces. If you see this, get it checked out by a professional or your local utility company just to be safe.