IAQ and a New Home

Weezbo

if say we wanted water in the kitchen and bathrooms and in certain fixtures ...and instead of specific paths of distribution we use a more "random"approach that incorperated uncontrollable leaks as part of the designe...now while you may indeed have water in the vicinity of the kitchen bathroom and fixtures it might not be exactly ...desireable. the same goes for the fluid Air in our homes. does this make it a little more clear than the information that you were previously given ? oki cool...*~/:)

Mark Adams

How tight can we go?

In talking to my E* rater guy, the question has come up of just how tight to try and make my new home. ASHRAE would like to see 0.35 ACPH. Between the builder (this will be a panelized home), the foam insulator, and the E* guy who does the sealing, I can get 0.2 ACPH without batting an eye. HMMM, IAQ issues. Actually, 0.2 equates to 3 people at 15 CFM / person for my house size.


The conundrum is obvious. Build tight, hydronic, add the ERV, then the AC. OK, way over budget now. Or, build loose on purpose, hope to end up at 0.35 +/- and be happy that no $2K ERV is needed. The other option is my original thought; FHA with all the bells and whistles and have enough left over for a new deluxe garden tractor.

How tightly are you gents building without going to HRV's? Does it sound crazy to build a bit loose?
I'd bet that the energy used to run the ERV + maintenance is a perfect tradeoff for the additional energy consumed due to a looser building.

Best regards,

Mark

Tom_35

We just tackled a problem tight house last week

The customer had built the house and done everything he could to make it extremely tight. Cellulose in the walls and ceilngs, caulk package, the works.

He then proceeded to put in too large of a heating and cooling system. The house was nearly 2,300 sq. feet and he had a 4-ton condensing unit and a furnace with a 5-ton blower.

Their call to us was about humidity levels being extremely high. They had 2 portable de-humidifiers running in the home, buckled wood floors, and vinyl that was rolling up at the ends.

A blower door test revealed that there is less than .2 ACH. Another HVAC contractor looked at the job as well and told the customer that if he would install a smaller furnce that it would take care of the humidity problem. The "old thinking" has been that might work, but the question is "where does the moisture go with the smaller furnace?" It doesn't just evaporate.

We have recommended that they consider a Therma-Stor de-humidification unit equipped with a fresh air intake duct. This house has got to breathe if the humdidity is going to be controlled.

If the customer elects not to spend the $$ for the Therma-Stor, we will recommend a metering air system to bring in fresh air and install a fan speed control to slowly bring in fresh air into the home.

Got to have several ways to look at fixing the problems.

Mark, I definitely would not "make it lose" for your air changes. Those AC's are uncontrollable while the things I've mentioned amount to controlled infiltration.

Tom A

victor441bsa

IAQ ventilation

According to your "flavor" of the international code, ventilation can be "built" into the structure by either natural or mechanical means. Unfortuntatly the requirements of make-up/combustion air are predicaded on its availability while the equipment is on line. Except for two pipe HVAC equipment combustion/ make-up air supply is an add-on for most jobs, i.e. openings to the exterior by one means or another, usually left open all the time even when the equpment isn't firing. Make-up air mentioned in the residential code is often neglected by everyone involved, make-up air is supplied to replace the air lost by various exhaust equipment. Other than the use of a simple thermal drop duct, cycling the supply of exterior air to the use point has always been a problem. The addition of exterior air in my climate NE michigan results in an extreme lack of humidity due to winter dryness, not to mention the impact exterior air temperatures have on comfort or customer awareness of cold air induced to his home,(if it is done without regard to all the implications of the net effect).
If you are experienceing an excess of humidity, I suspect either the building site itself, (is the house built over a swamp, and has no moisture control in the crawlspace/basement?) or is there no means of exhausting "life" generated moisture (cooking,Baths,showers)?
Has the mechanical contractor/builder ignored the fact an ordinary clothes dryer has the run-time and sheer power -2"wc @ 200cfm or higher, to remove all the air in the structure in less than an hour in many cases. If one takes into account the average draft of 'B' vented gas fired equipment-.02wc, the dryer is 100 times stronger and will get its make-up air down an operating space heating boiler/water heater chimney, sometimes tragicly introducing combustion products into the dwelling due to the lack of combustion or make-up air availability.
ERV's are wonderfull things except for one small problem, they are balanced, they bring in exterior air and push out interior air at exactly the same rate, they do not bring make-up air into the dwelling to relieve the vacum caused by exhaust equipment and relieve negative pressure,on an as needed basis. Exhausts cause negative pressure allowing the house to inhale or retain moisture from where-ever.
Building tight is where america is at, cus we are afraid of heating costs, deal with it. If the Builder/homeowner/designer causes this problem, the heating guy will have to solve it, just like always.

Mark Adams

Weezbo, Tom and Victor

All superb replies. They all get right to the heart of the problem(s).

New homes are notorious for high moisture levels for 6-12 months after being built. This adds to the normal moisture problems. And this begs for balanced ventilation to get rid of the problem in addition to spot ventilation for the kitchen and baths.

So where does this all lead? Do I have a secret agenda? Kinda. Like almost everyone, 1) I'd like to lower my energy cost, 2) I'd like to have superb IAQ (I'm familiar with this as I do IAQ investigations at my University and we have about 100 buildings) and 3) I'd like to only spend up to the Buick level, i.e. more than the Yugo and less than the BMW.

When I referenced building loosely on purpose, I mispoke. I meant, build to present energy * levels using the current standard techniques. Simply NOT going the extra steps to foam and caulk everything. And yes Weezbo, I do get the controlled ventilation arguement. But to me, unless this means ducts and controlled air flow going right where you want it, well, it's back to "uncontrolled leakage".

Victor, it sound like our climates are very similar, I'm in WNY. FWIW, my initial shot at addressing all this was to build tight, go PROPERLY SIZED FHA with A/C and ERV and conditioned intake to account for point exhaust. In fact, I think if you build new in the vast expanse been us known as Ontario, you MUST have an erv/hrv per code.

OK, my point with all this is, if you build a new home you are FORCED into FHA! Tighten it up and you've got IAQ problems to solve. Don't tighten it up, and it may end up to tight anyway. To tight? Add an HRV. Oops, bath fans and dryer and kitchen exh need makeup air so let's add an AprilAire VSC. Hmm, gotta add A/C for summer, where is all this ductwork going to go??

Thanks again guys, this is FUN!

Mark

hr

Build it tight, and ventilate it right!

Keep in mind you will need to condition the space including possibly humidification, dehumidification, air exchange and allowance for any exhaust fans to operate, filtration, etc. And of course a comfortable, hopefully radiant, heating system

Yes, it does get to be a big $$ number to do it right. If you plan on living there for some time, I believe I would find the money to build the best possible home comfort system.

Check out www.healthyheating.com for some great info on "big picture" thinking.

hot rod

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