Super insulated house and ventilation

kevin coppinger_4

would be Renew-aire. I have used a coulpe and they appesr to me to be a beter product..not that Lifebreath is bad...kpc

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Wayco Wayne_2

Working on

my customers house who is about to use icelyne foam. The plan is to make the houe supertight. I am considering how to control the air changes and the bathroom exhaust fans and such things. We are going to use an HRV to recover conditioned air. I need the basics for design, perhaps recommendations for equipment and references to educate myself. We are close to being done with the radiant floor and boiler. I will have pictures soon. WW

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Brad White_9

I like Lifebreath products

Made in Canada, eh.
But there are others too.

The Icynene will indeed make a tight house and you are being diligent about this, Wayne. Lifebreath has pretty good literature on the principles. Canada has a lot of code references about ventilating these kinds of homes; they take it seriously.

The standard I use is 0.35 air changes per hour as a minimum background value.

(Volume x Air Change Rate)/60 minutes = cfm

So a 2,000 SF home with 8 foot ceilings = 16,000 CF volume.

(16,000 x 0.35)/60 = 93.3 cfm.

I may add to that for known intermittent exhausts such as a kitchen hood but that would be a separate make-up system. No recovery from the kitchen hood. It gets messy and not worth it for the time it runs.

In addition, I want to make sure I have at least 15 cfm of outside air per person, 20 if I can. Just a cross check, usually I am OK with the Air Change method.

Naturally you want to exhaust from less-clean areas (bathrooms of course) and supply if possible to any central air system return. This will absorb the temperature losses.

If no air system, I tend to supply rooms where a clothes dryer occurs as a form of make-up air. (This in addition to NFPA-54 requirements, high-low grilles and all that.)

The highest efficiency units (talking flat plate sensible only here) have two (2) exchangers in series and can reach 90% sensible recovery.

If you have humidity issues, the dessicant wheels are the way to go. High latent and sensible recovery. I use Airexhange made near me in Norwell, MA. They make OEM wheels for several manufacturers. There are a number of other manufacturers out there too.

Hope this helps-

Brad

S Ebels

What Brad said

Another excellent HRV is Ultimate-air. I've used a few of theirs along with LifeBreath. Both are good but I like a couple things about the Ultimate better. It's a US made product and distribution is much better. I've had replacement filters on order for a LifeBreath TFPC air cleaner for 3 months. Still don't have 'em.

Wayco Wayne_2

Here's a pic

from "Squirrel House" so named by the Homeowner who as I've reported before started working on remodeling his bathroom and ended up gutting the house. He will be spraying icelyne foam soon. We have a Munchkin 140M working the basement zone which is pex in slab on top of an inch of blue ectruded styrofoam. I have the control wires jumper so boiler always has demand and the temp set at 100 F. It's nice to have a spot to go warm up after pounding pex and plates in the unheated crawlspaces of the other zones. WW

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Constantin

Good Points...

... all I'll add is that when you select an HRV or ERV, consider using one that can achieve the rated ACH at its lowest setting so as to make it as efficient as possible. Then kick it up to exhuast the bathrooms at 100CFM/bathroom when needed. That eliminated the bathroom fans from our home.

One unit that Jerry Scharf alerted me to is the Sterling Tech ERV, which looks like an amazing unit. Had our Lifebreath TRVs not arrived soon after, I would have gone for this unit instead.

Wayco Wayne_2

Brad

Thank you for such a complete dissertation on the subject. It took me a while to digest but it all makes sense to me now. I will exhaust from all of the bathrooms and supply back into the return duct. I think I can do it all from the attic best. The attic is accessable with fold down steps too. How do I initiate and how long do I run it. Fortunately I have a variable speed air handler upstairs that can run at a very low speed in the Winter to distribut the fresh air. Since that heating system is radiant floor it won't be running in the Winter otherwise. Do I tie into the bathrooms with a spring wound switch for exhaust or just run on a timer, or do I run all the time???? Funny how a little knowledge breeds more questions.

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Wayco Wayne_2

Constantine

Thank for the unput. When I click on your link for Sterling I get the Ultimate ERV web site. Is this a mistake or are they one in the same? WW

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Constantin

That's the right unit

Why they sell a product on a web site whose name has little to do with it is something I'd discuss with the marketing department. Jerry really liked the Sterling product for several reasons:

• Since the replacement parts are standardized and hence somewhat immune from the gouging and supply issues that can allegedly plague the Nutech product lines. For example, several contractors have reported Lifebreath parts being delayed for months.
  
• The Sterling unit recovers 93% or more of the energy (!!!)
  
• As an ERV, it'll help keep the humidity inside during the winter and outside during the summer.

I was too far along to get them, as we had already built the areas up to hold them. So, I have two Lifebreath TRVs which contain one HRV core and one ERV core. So far they have worked well and the bathrooms evacuate without any issues.

Once I have the occupancy sensors dialed in (they activate the high-speed mode and duration of the TRV) I may even be able to reduce the fan speed when evacuating the bathrooms. The acid test is the furthest bathroom from the TRV, right?

Constantin

Here is how I did it...

... which doesn't mean it's right.

The Lifebreath TRVs were sized to meet two loads. Under normal conditions (i.e. no bathroom occupied) they were programmed to run 100% of the time to achieve 0.35ACH while exhausting from the bathrooms only. When the unit kicks into high-gear during occupancy, it flows at 100CFM, which is enough to exhaust clouds of shower steam and surface condensation on windows, etc. in less than 5 minutes.

Some inexpensive Leviton ceiling occupancy sensors (normally used for lighting applications) in conjunction with the "power pack" allow you to close a contact on a 120VAC-rated relay whenever a room is occupied. Best yet, all the wiring between the power pack and the sensors is 24VAC, so you don't need a electricians license to install it (my contractor loved that!). The Power pack also generates the 24VAC from the line voltage.

Anyway, so the contacts from the relay can pass any voltage up to 120VAC, or none at all. In fact, the Lifebreath controller only wants a dry contact (i.e. continuity vs. no continuity), so you simply wire the two red wires out of the power pack across the high-speed terminals on the lifebreath controller and you're done.

Now you go back and adjust which sectors the sensors are sensitive in (i.e. walking by in the hallway is probably not a good reason to start), the delay (they can "run" for up to an hour after the last movement was detected, IIRC), etc. I have not yet dialled in mine, but keep sensor placement in mind when you discuss bathrooms with clients. Some are very sensitive to things sticking out of walls, etc.

What I like about the occupancy sensor/delayed timer approach is that it's effortless on the part of the user. No one has to be trained to hit a switch, turn a timer, etc. so it's one less thing that is forgotten. Perhaps some day affordable humidistat/occupancy detectors will make their way down from the likes of Panasonic who already have them in their bathroom fans into discrete units to control HRVs...

Anyway, credit for all this will go to someone special at Nutech who was kind enough to point me in the right direction for inspiration.

Brad White_9

'Morning, Wayne...

Awww, 'twas nothing really

In turn, I learned about a new product line in this thread. I have used Lifebreath for about eight years and own one but obviously have to keep up with newer products. I will check the Sterling and Ultimate product line.

I would caution against installing the unit in the attic if unheated because of condensation freezing. Lifebreath says not to put them in attics for that and other reasons (ease of service I believe). May just be a limitation on the product.

For controls in a house-wide system, there are packaged controls (again, Lifebreath is my limited reference point) that I imagine are offered by others.

Here are some options in common local controls:

Cycle by timer (hour on/hour off or constant run day, off at night, all adjustable)

Twist timer (bathrooms mostly)

Indoor humidity (bathrooms and general house)

Motion detector (bathrooms and/or general house).

You can set these up in parallel as "this OR that" control such that any one will operate the unit. "Ladder rung control".

Some standards recommend running all the time but I see that as wasteful. Best part about the programmable controls is that it can be adjusted to the lifestyles of the occupants.

For mine, I have a twist timer in the bathroom plus it responds to high humidity. It is also tied in to the dryer as make-up air via a Veris Hawkeye current sensor tied to the dryer circuit. Dryer runs, make-up air is on. (I have my laundry on the second floor in the only interior room in my house so need combustion air by code.

And my bathroom mirror, when it runs even on low speed, will never fog. Dries in a snap!

Brad

Constantin

Ahh, but not all attics are alike...

... if this customer elects to icynene the rafters, then the attic becomes part of the conditioned space. No freeze-ups to worry about. The only "concern" could be a supply of warm air to defrost the unit with if you're in a very cold climate and don't elect to pre-heat the incoming air.

Brad White_9

Agreed.

Just have to define the envelope was the point I should have made.

Thanks, C!

Brad

Mike T., Swampeast MO

Aren't you in the D.C. area Wayne?

If so, I believe an energy recovery ventilator (ERV) is more suited to the climate. Don't believe they're quite as efficient as HRVs in cold weather, but they reduce humidity brought in during warm weather. Heat recovery ventilators (HRVs) are generally used in climates where heating predominates--not cooling or well-mixed climates.

Wayco Wayne_2

agreed

I will modify my vocabulary. I mean to say ERV's. Also the attic is inside of the envelope in this case so the ERV could reside there quite nicely. Thanks for all the good info. Now I'll look like I know what I'm talking about to the customer. WW

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Wayco Wayne_2

Thought I was done

didn't you? I have now educated myself enough to be trouble. Perhaps. I am planning on drawing air from 4 bathrooms and mayby one from the attic space. We're worried about moisture in under the foam up there. How do you size the duct work. The unit has 6 inch connections but can move 200 cfm that's 8 inch size for normal duct sizing. The on line manual says no branch should be smalle than 5 in, but if I'm dividing the exhausts coming from the bathrooms and attic I can go 4" by my ductcalculator. Please finish filling my head with info. WW

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Brad White_33

Duct Sizing

Provided the ductwork is well sealed and insulated, no harm in up-sizing a tad. You are correct in that the 6" connections are small for "travelling" size. 8" is, to me, tight for 200 cfm; I generally limit that to 175 to 180. Definitely transition from the opening side. Use conical transitions not the hard-edged "bushing" types. If the connections are close together on the unit, get eccentric type transitions.

(Point of Information: We are talking rigid sheetmetal ductwork here, not flex! Flex duct should be at least a size or two greater than if hard duct and is subject to "shortcut abuse", twisting and forcing it into contortions unmentionable in a family program.)

Here are my guidelines for duct sizing (admittedly conservative but you are building it only once, right?)

Smallest duct size for "travelling" (not final connections at either end: 6 inches is my personal practice. Off of this you can get (2) 4" taps for those small round diffusers. Gives you flexibility.

That said, reality kicks in:

4" = 30 CFM ("Metric Squirrel Fart") Hardly worth it IMHO.

5"* = 50-60 CFM (450 FPM max. and 0.075" per 100 feet PD)

6" = 60-90 CFM (460 FPM max. and 0.070" per 100 feet PD)

BTW: 3.25 x 10 stack duct is equal to 6" round.

7"* = 90-130 CFM (450 FPM max. and 0.075" per 100 feet PD)

BTW: 3.25 x 14 stack duct is equal to 7" round.

8" = 130-180 CFM (450 FPM max. and 0.075" per 100 feet PD)

9"* = 180-250 CFM (575 FPM max. and 0.075" per 100 feet PD)

10" = 250-350 CFM (650 FPM max. and 0.075" per 100 feet PD)

The sized I marked * are ones I rarely use and skip over to the next even size. Just a preference but offered in case you have a fit issue.

Use wye fittings instead of hard tees, make it easy on the air.

If you have a sketch layout or description with dimensions let me know and I can calculate a SP profile for it.

Brad