A lot of old timers don't understand the why's of air sealing in current construction. Building Science Corp. has a lot of info dealing with air sealing, moisture control in wall assemblies, etc. in their tech resource section. On our new home, I chose to establish the air barrier at the foam sheathing on the exterior wall because there were fewer penetrations to deal with. Also went with 1" foam sheathing, which by a BSC article, insures that moisture will not condense on the 'cold' surface of the foam in my wall assembly. Also spec'd an outside air supply to beintegrated into the HVAC system. This uses a Honeywell controller to determine when outside air is needed within the home.

Here is a link that might be useful: Building Science Corp - Tech Resources

I bet you heard the following: "Your house needs to breathe." You can't build too tight." And the clincher: "This is the way we always do it."

Stick to your guns. And if you're getting a designer, have him/her specify what you want. That way, the trades follow the plan or don't get paid. Amazing how fast they "learn" when it's put that way.

I am having a house built right now that will have a geothermal system too. It is critical that the house be sealed and insulated correctly (that means tight) to make sure the HVAC system will work properly. GT is great, but it won't work well if your air infiltration is too high. You need fresh air too - so make sure the HVAC people include an air ciculator which will bring fresh air into the house peridocially.

I got a lot of useful info from a TV show done on the DIY network last year. Check www.diynetwork.com and do a search on "Home IQ" and look for the series on the Oberg Family. They have videos that you can watch online that explain the process they used - it was very informative.

I would also suggest doing your homework on the foam insulation. Look at the various types of foam - and also look at the cost compared to other insulation methods.

Good luck.

As suggested, the Building Science website has alot of good information. Our area is very resistant to changes in building methods/materials and we too heard "that's how it's always done" especially when we insisted on the windows being flashed correctly. We persisted to have it done the way we wanted. We heard less on the foam insulation as they seemed to be much more curious too see it.

thanks folks - Appreciate the info and the links.

What do you mean by flashing the windows correctly..?

thanks

Check out the details at the American Plywood Association's (APA) site.

Here is a link that might be useful: Buildabetterhome.org

You can't live well without fresh air especially in this age of untested synthetic materials so a tight house can definitely be a serious health problem.

What is essential is a heat exchanger that transfers heat from exhaust air to intake air.

Here is a link that might be useful: good ventilation in a tight house

I would be concerned about trying to get builders who have not been building "tight houses" to build that way for you. The statement above that "your house needs to breathe" is quite true--there needs to be a way for any water that gets into a wall to get back out again. There are many homes that have been built "tight" in recent years that have literally rotted out within a few years because they were built such that water got trapped inside the walls.

You can't just arbitrarily go and "seal" things and expect to have a durable structure. The science of how to that correctly in a wood-framed structure is quite complex, and is unlikely to be understood by "traditional carpenters" who don't want to build that way.

If you want a "tight house", find builders who have been building that way for a decade or more, and have made the mistakes on somebody else's homes. (I guess that sounds a bit crass, but infinitely preferable to having your own home rot out.)

We build pretty tight around here. In the testing I do it iw not uncommon for a home to meet the minimum requirement of .25 air changes per hour.
the key to a healthy house is to know when this minimum requirement has been met & deal with it accordingly.
Build tight & ventilate right.

While you don't state the age of your house or location, in existing homes air tightness was not an issue until the mid 70's. If your home is older than this, you may have quite a way to go air sealing ways before meeting a low enough air change rate to require a fresh air/make up air addition.
By adding on the the back of the house and opening up for a second story you have access to a lot of areas to seal that you would not normally have. You also have the potential to create more leakage sites.
You would benefit from a blower door test prior to renovation, a test mid way of air sealing, and a final test one work is done to catch any missed areas of infiltration.
Even then a fresh air intake may not be needed. but unless you test..to find out where to seal, and where you start off & where you end up...you will not know if your methods were cost & labor effective.

best of luck with your project.

If you rely on an air barrier membrane like a house wrap to reduce air infiltration be aware that the claims for its effectiveness are based on the testing of houses where it is wrapped under the foundation plate and over the top rafter plate and sealed at all joints including the horizontal ones that are almost never sealed by contractors even if they have read the installation instructions which I suspect most have not. It is rare to find a contractor who has any realistic understanding of this subject.