Satisfying ASHRAE 62.2 when installing a hydronic heating system

Jed_2

That's pretty healthy, considering a radiant heating system, and a 65-70% effectiveness. In most cases, that puts you into a supplemental status. So, what is a good "zero ventilation heat balance" strategy? Electric resistance, hot water coil, supplemental radiation?

Not being an Engineer, and relying on manufacturer's ACH guidelines, I've been using .35 for HRV sizing. Am I missing the boat? And that number creates problems at the typical effectiveness rates for HRV's and plated joist panel outputs. And, yes, one really needs to know the real numbers for the installed household ventilation equipment. And, if you don't know that total; go to the .5 ACH rate?

I thought it was 15-20 CFM per person for residential.

Thanks

Jed

James Healy

What is common practice to provide ventilation under ASHRAE 62.2 when installing a residential hydronic heating system?

GMcD

Residential ventilation and ASHRAE

My normal practice as a design engineer is to use an HRV or ERV depending on climate zone, and size the HRV for the greater of any of the following:

- Make-up air for exhaust sources (dryers, range hoods, bathroom exhaust)

- 30 cfm per person based on average permanent residents.

- Local Code minimum air change rates (usually around 0.5 ACH)

That being said, the dominant ventilation/make-up air requirement is for the exhaust sources in the house. Granted, not all of them will be on at the same time, so there are a couple of different ways to deal with it - the range hood is a high cfm, but intermittent exhaust source, so generally on the higher end homes I'll have a small HRV interlocked to the range hood to provide make-up air for the kitchen only. The rest of the house is served by a central HRV that is controlled by interlocks to bathroom exhaust switches, humidistat(s), and a timer. I don't mean to imply that there would be discrete bathroom exhaust fans, but you duct the exhaust from the bathroom through the HRV so your HRV is actually your "exhaust fan" for bathrooms and that's what the bathroom exhaust switch would control.

I tend to use more ventilation than ASHRAE and Code, since, to me, the Code is a minimum standard- below that, you're breaking the law, but there is nothing wrong or bad about exceeding Code, other than watching the additional energy costs to do so.

Unknown

You also in addition

to Geoff's air requirements may need to provide additional air for combustion for the fossil fuel burning equipment. There also is requirement for sufficient air to keep the boiler room temperature at code.

I prefer air for combustion for equipment to be provided by mechanical means with interlock to shut down the equipment if air flow is not proven.

There may also be a need to provide a Star-Kap for the vent system along with blocked vent switch to insure shut down if spillage into the building takes place which would definitely affect air quality.

The final thing is to have smoke and CO detectors in place to alarm if air quality is below standard. In the case of the CO detector a low level 10 PPM alarm detector is preferred.

Finally a stable humidity level is required.

GMcD

Gas stoves and ranges

Geez, yer gonna get me all fired up about all the high-end condos and houses with the big honkin' gas stoves and ranges, and little to no combustion air or appropriate cooktop venting. The Codes are quite far behind the reality these days with near commercial level gas cook tops, ranges, and stoves getting installed in 800 SF high rise condos with little to no fresh air or ventilation in them. It's scary, but I have even been asked "what's the worry?" by the local gas utility. In addition to the smoke detector and/or sprinklers in these places, they ought to have mandatory CO detectors....

Unknown

Have the local utility

give me a call and I will give them something to think about. The gas utilities used to be at the forefront of code enforcement but things have changed. It was once a policy that even if the code was non-existant or vague they would still at least lean on the side of good common sense or past exoeriences with problems. Even the ANSI standards which allow 800 PPM to vent from gas oven vents or the 400 PPM in flues for water heaters, furnaces and boilers is insanity to say the least. For those reading this who want to know what should be allowed the answer is under 100 PPM for heating and hot water, 25 PPM for gas ovens. While we are at it how about allowing 200 PPM for unvented space heaters. Somebody should wake up.

GMcD

Climate dependent

Jed: the ACH is really a local climate dependent application. In a cold heating dominated climate where I'm from, the issue is humidity control inside the house during winter to prevent condensation inside the envelope, as well as maintaining a minimum level of humidity for healthy conditions. The Part 9 Residential Code (Canadian Building Code) uses 0.35 ACH as a minimum. That can't, and shouldn't be applied "everywhere" due to extreme climate differences and types of house envelope and occupancy. Down in the SE United States, it's a completely different ventilation requirement and humidity control requirement. It's very climate specific and 0.35 ACH doesn't cut it in many of the more extreme climate zones of North America.

In my area the high end homes are usually associated with a lot of entertainment and cooking, generating lots of indoor humidity, so the higher the ACH, the better you can deal with the occupant's transient humidity loads. After all the HRV is only gonna run from what the room humidistat is set for, or the timer, or whenever someone takes a bath or shower and uses the bathroom exhaust to keep the fog off the mirror.

Personally I use 0.5 as "good practice" design. Yes, some supplemental heat is required for the HRV, the colder the climate, and it's easy enough to use either an electric coil or a fat heating coil piped with the low temperature radiant supply water to keep it simple. You need some supplemental heat off the HRV/ERV anyway during defrost cycles in the colder climates anyway. The Bean has some "good stuff" on more science back-up for more and proper ventilation in a radiantly heated/cooled space over at HealthyHeating.com.