I'm building a well insulated tight home with 2" polyiso exterior foam and 2x4 dense cellulose walls with R50 cellulose attic insulation. This is being built in southern Ohio. We have probably about  6-12wks of cold temperatures that require heating beyond a heat pump. I plan to install a basic wood furnace to help offset the cost of electric resistance heat sticks for the cold days of winter. With this tightly built home I'm concerned about air intake for the fireplace. I've read alot about ventilation systems HRV/ERV and they seem complex and if not done right seem to cause more harm than good. I'm concerned that our local contractors simply don't have the expertise to do the installation properly and to call an expert in seems cost prohibitive to me. I'm wondering what the thoughts of a more simplistic approach would be. I have a large two car garage built onto the home 30x26 and garages are very leaky air wise. This is due to the nature of garage door sealing and the fact that those large doors are opened up when cars enter and exit. An insulated garage attached to a house seems to keep a temparature of around 55 degrees in my area when it can be 0 outside. All of that said, for the sake of a more simplistic ventilation system could I run a straight vent from the garage to my furnace to allow ventilation into the house at  55 degree temperature oppsed to the colder outside temperature. In addition to this upper level two car garage I have a basement garage that will also be letting air through it. Perhaps this will just naturally ventilate my basement, but the basement garage will be walled off and I know the basement garage is the weakest point in my tight home, it is a R16 door and seems well sealed. Just wanted to get thoughts/suggestions on this idea or other more simplistic ventilation options. I've known some local people who have built ICF homes and  fully spray foam homes that have not installed the ventilation systems being this seems not widely adopted in my area i'm learry to dump 2k+ into some sort of ventilation system.

Venting from the garage is not recommended and illegal in my area for all the fumes from cars, lawn tractor ,etc,
will enter your home and make for a not so much clean air environment.
Air change devices are imho a good investment however you could get away with an open window if you don't mind the cold season. My hrv also eliminates humidity from the outside air as it comes in.
Is this to acheive air changes or simply to make sure the stove does't create negatives.

This is bad way to pull exhaust fumes into the house. Not likely to pass code in most Jurisdictions. Think about all the chemicals and gas for lawn mowers, etc in the garage. I don’t even like having common walls between garages and the house for this very reason. I kind of like them separated by a non airtight breezeway or just plain detached.
If you are worried about the woodstove in particular, you can use one that has an outside air supply kit. On the other hand a wood stove has a fairly small air requirement that is not likely to cause problems unless other exhaust ventilation is on, depressurizing the house.

You will need some source of fresh air.

Cheers,
eric

Thanks for the contributions and I would agree that in a genaral sense these are all good points, however, I don't intend to store lawn equipment in this area and am not one to leave a car running in the garage longer than it takes to back out. All said I think there is nothing better than an attached garage for convienence, sure there is additional risk, but there is with about anything and everything. Alot of people don't like wood burning fireplaces internal in the home for the same sorts of reasons. I guess really more than the concern for ventilation to my stove is my concern for the house as a whole, while we have done due diligence to make the house tight and well insulated we have not went to extremes such as blower door testing and spray foaming every possible junction point on the house. Cellulose is not going to be as air tight as spray foam and I also realize that the 2" polyiso although taped and gap sprayed with foam will still not be as air tight as a full spray foam system or ICF. I'm hoping I have enough natural ventilation to not warrant the need for a HRV system, but want to best set myself up for options down the road should a further problem expose itself. Based on my configuration do you guys believe I need an HRV unit? The suncourt HRV unit seems most cost effective at $400, but I'm sure installation drives it upwards of at least 1K to get it put in + future maintenance and power consumption of unit.

I do believe you need some sort of air changing unit.
Old, leaky, unefficient homes don't but from your house description, if it would be me ,I'd put one in.
At my place when it kicks on, more in the winter months, it's just like stepping outside and taking a breath of fresh air, seriously!

Posted By kschweitzer69 on 16 Dec 2010 01:51 PM
Thanks for the contributions and I would agree that in a genaral sense these are all good points, however, I don't intend to store lawn equipment in this area and am not one to leave a car running in the garage longer than it takes to back out. All said I think there is nothing better than an attached garage for convienence, sure there is additional risk, but there is with about anything and everything.

The problem is that you may not always own the house. Codes are there to protect more than the immediate owner, but any future owners. I'm sure you would feel bad if you sold the house and learned that the new owners were made ill or killed because of a "easy shortcut". If something is worth doing it is worth doing right.

Posted By kschweitzer69 on 16 Dec 2010 01:51 PM
Thanks for the contributions and I would agree that in a genaral sense these are all good points, however, I don't intend to store lawn equipment in this area and am not one to leave a car running in the garage longer than it takes to back out. All said I think there is nothing better than an attached garage for convienence, sure there is additional risk, but there is with about anything and everything. Alot of people don't like wood burning fireplaces internal in the home for the same sorts of reasons. I guess really more than the concern for ventilation to my stove is my concern for the house as a whole, while we have done due diligence to make the house tight and well insulated we have not went to extremes such as blower door testing and spray foaming every possible junction point on the house. Cellulose is not going to be as air tight as spray foam and I also realize that the 2" polyiso although taped and gap sprayed with foam will still not be as air tight as a full spray foam system or ICF. I'm hoping I have enough natural ventilation to not warrant the need for a HRV system, but want to best set myself up for options down the road should a further problem expose itself. Based on my configuration do you guys believe I need an HRV unit? The suncourt HRV unit seems most cost effective at $400, but I'm sure installation drives it upwards of at least 1K to get it put in + future maintenance and power consumption of unit.

Your house isn't tight unless it's proven tight with a blower door test.
A blower door test is not an extreme.
Backing your car out quick is a poor reason to rationalize a "fresh air" intake from a garage.
Because you have not looked at every junction point on the house it's probably leakier than you think.
If you're relying on enough natural ventilation to warrant no HRV your house isn't tight.
If you spent the money on a tensioned slab for a basement garage don't complain about 2k; unless of course you housed the basement garage inside the wood framed structure which would then be a design flaw.

Some food for thought.

Greentree-All points well taken. Please link to a previous thread on my house that will give you a few pictures to get an idea of what we have: http://www.greenbuildingtalk.com/Forums/tabid/53/aff/14/aft/78008/afv/topic/Default.aspx
I agree with the point that the house is not tight unless proven with a blower door test, but at least in my area I'd consider it an extreme as it's certainly not the norm when building new homes. Not to mention I'm not sure how you can adequatly execute a blower test until dryall and insulation are installed and at that point how do you address leakages. A house that naturally ventilates is generally considered inefficient, but I simply don't know where my house will stand in the end. I have a feeling that if I don't install a HRV I'll get moisture buildup on the windows due to insufficient air changes. I"d have to think the cellulose/polyiso is going to be a good combination to insulate with, but how much air leaks through I don't know as stated we taped and foam sealed joints and taped OSB sheathing seams. As far as the basement garage goes I know it's a weak point in designing a tight home. I'm not sure what a tensioned slab is. I think the latter part of your statement applys the basement garage is part of the overall house. In a general sense I agree with all comments pertaining to gathering fresh air from upper level garage. Fumes, etc seem to be a valid concern. Now it's back to the point of wheather I should install a HRV/ERV.

HRV/ERVs are not your only ventilation option. on the cheaper side you could install an exhaust only tipe of ventilation using only bathroom fans and passive air inlets properly positioned (search for robert riversong projects) but that is not an easy task to design properly.

I don't understand why you consider HRV complex. Some of todays HRV/ERVs have automating balancing of the intake/exhaust all sorts of fastening devices for the ducts and the manufacturers intallation manual are very clear and nothing seems very complex.

good luck
adi
http://torontonetzerohouse.blogspot.com/

I would not want a tightly sealed garage - at least not when it is wet (from wet cars, ice, etc). Let it dry out before everything rusts.

Posted By kschweitzer69 on 16 Dec 2010 01:51 PM
Thanks for the contributions and I would agree that in a genaral sense these are all good points, however, I don't intend to store lawn equipment in this area and am not one to leave a car running in the garage longer than it takes to back out. All said I think there is nothing better than an attached garage for convienence, sure there is additional risk, but there is with about anything and everything.

Makes no difference. The International Residential Code, which probably applies to you, absolutely prohibits any sort of ventilation for living space or combustion coming from a garage. You cannot even run a duct from your heating system into the garage. The garage/house barrier must be sealed, top to bottom, with no penetrations except doors which must be self closing and fire rated.

In your first post you mention both wood burning furnace and fireplace. Are you putting in both, or just a fireplace? In any case you must have an adequate air supply from outside, either with an air supply duct to the fireplace or a mechanically ventilated room. Here's the quote from the 2006 IRC.

R1006.1 Exterior air. Factory-built or masonry fireplaces covered in this chapter shall be equipped with an exterior air supply to assure proper fuel combustion unless the room is mechanically ventilated and controlled so that the indoor pressure is neutral or positive.

R1006.2 Exterior air intake. The exterior air intake shall be capable of supplying all combustion air from the exterior of the dwelling or from spaces within the dwelling ventilated with outside air such as non-mechanically ventilated crawl or attic spaces. The exterior air intake shall not be located within the garage or basement of the dwelling nor shall the air intake be located at an elevation higher than the firebox. The exterior air intake shall be covered with a corrosion-resistant screen of 1/4-inch (6 mm) mesh.

I'm afraid this is one area of your house construction you cannot cut corners on. You must do it correctly or it won't pass inspection. If you opt for an HRV you will need to have a pressure switch on it so when you light up the fireplace it will sense the pressure drop from the draft and turn on.

dmaceld - well said! I would add that air exchange is not just about moisture control. There are many other pollutants inside a house. There is always some out gassing no matter how green you built. Then there is all sorts of products used in the house during normal living i.e. hair spray, shoe polish, cleaning supplies. Every person in the house is using up oxygen and the list goes on. If you can not get at least 1/3 ach from your windows and fans, you need mechanical ventilation. And it should be run of a timer not a humidistat. In Alberta many houses are so dry inside that a humidistat would never call for ventilation yet the air is very stale.

Here in Washington State, the regulations for wood (and pellet) burning devices are even more strict than the EPA regulations.  ALso, I am not an expert on this at all, so, for those reasons forgive me if I make some statements that don't apply in other states.

The regulations exist to control emissions, but with that comes increasing efficiency.  The idea is to burn the fuel (wood) and then effectively reburn the flue gases that are normally lost up the stack.  Because houses now can be built very tightly, it would be difficult to engineer a wood-burining device that could reliably do this considering the various ways in which it would have to draw combustion air.  For that reason, (and code mentioned previously), all these units I have ever seen have combustion air supplied from an outside source via a duct, within certain parameters.  Of course, the final exhaust must go up a stack just like any other indoor burn.

If it is a free-standing unit, the walls of the stove heat up and the interior is warmed in this manner.  However, some units have interior plenums, I guess you would call them, in which air is HEATED and them moved via fan to outside the stove.

With the fireplaces and wood stoves many of us might have grown up with, the COMBUSTION air was drawn from within the house.  A pretty large volume was required for that and it would effectively depressurize the home, drawing in outside cold air from every crack and seam.  It was most notable in far reaches of the house, where air was being drawn in and where the heat from the wood-burning unit didn't reach.  That is the last thing you want.

At the very least, you want a unit that uses outside air for combustion and warms the air in your home.  Just the act of warming the air in your home should create a slight positive pressure inside which can help stop the cold air infiltration and drive warmer air to the farther reaches of the home.  The increase in fuel burning efficiency is probably worth it.

Some of the larger units have the capability of drawing the HEATED air from outside which creates a much stronger positive pressure and can help drive the heat to farther corners of the home.  You can also elect to position this intake via ducting inside a far corner of your home which creates a flow of HEATED air from the unit to the intake without pressurizing the entire interior of the home quite so much.

I don't think the HRV/ERV is going to do much for you unless you can show that your home reaches a certain level of tightness.  After that, you control (balance) the air exchange in your home (which is one of the biggest heat losses) using the ventilation unit.