IAQ considerations while installing heat pump?

[alota hvac]

I'm totally new to the subject of HVAC, so I'm looking for some advice (I think I came to the right place)...

We have a 2650 sq.ft. 2-story home in Montreal. We have extreme seasons - insane winters and hot humid summers. The home is 5 years old and has a York 5 Ton, 2000 CFM Air Handler (N*AHD2006A) plus a LifeBreath 200MAX HRV. We're in the process of getting bids for a Heat Pump (I'm considering either a York Affinity 3S or a Lennox HPX15, HPX16 or XP19). Any recommendations on this as well would be appreciated, but my question is more about IAQ.

I'd like to take the opportunity while we're installing the heat pump to do anything else that will help our air quality. We have a dog and a cat that produce odors, and our basement is humid and musty (we have a open sump that usually has standing water in it). We live in a wooded area with a LOT of pollen. Apart from getting rid of the pets, is there anything else we should install in our HVAC system to reduce humidity, reduce odors and reduce dust & pollen? I'm willing to spring for a Lennox PureAir and/or a HEPA Bypass system if it will make a difference. I don't know if the Heat Pump will reduce the humidity enough. Any advice?

Thanks in advance

[teddy bear]

Make it simple. Controlling the %RH to <50%RH eliminates the odors and mold. During cool rainy weather, the hP responds to the temperature not %RH. Cool basements require small industrial dehumidifiers like the Ultra-Aire/Santa Fe. You need 100 pints per 2,500 sqft of space. These units are capable of maintaining <50%RH if the windows are closed. Also suggest a little make-up fresh air ventilation(50-75 cfm)to purge the home of indoor air pollutants during the warm time of year. The items you mentioned treat the symptoms(odors) rather than the cause (mold growth). Your a/c contractor can deal with the details.

[alota hvac]

Hi TB,

Can you explain "make-up" ventilation? Is that what my HRV would provide, or do I need another device? Can I run my HRV all day long, even during the humid summer? Also, I have some doubts about my HRV's ability to exchange the air in my basement, because the HRV return air ducts are installed near the ceiling between the kitchen/powder room on the 1st floor, and in the two bathrooms on the 2nd floor. I don't see how basement air is being exchanged (unless I run the furnace fan as well to circulate the basement air into the house).

Thanks.

[drk]

Space guard to remove pollen and pet dander/hair. Buy a 60 pint dehumidifier for your basement and cover the sump.

[teddy bear]

HRV is great. Discharge some of the HRV's air into the basement if in doubt of the circulation of the fresh air. You must control the amount of fresh air ventilation. Suggest 50-70 cfm of fresh air ventilation when the home is occupied. This is 50-80 pint per day moisture load to maintain <50%RH. Regarding the size of dehumidifier, you need enough capacity to maintain <50%RH throughout the home. Get one good dehu or several small reside dehus. The problem is that resid. dehus do poorly at cool basement temperatures and remove a fraction of their rated capacity. If in doubt, try a resid. dehu and monitor the %RH. Most homeowners try a cheap resid. dehu. solution before being convinced that they need a real dehumidifier. You need to remove a minimum of 70-80 pints of moisture every day. The Santa Fe uses 6.8 amps removing 4 pints of moisture per hour, the most eff dehu made.

[drk]

Most people buy more dehumidifier than they could ever need. My basement is 90% under ground no tar on block very little drain tile built in the 60's. 1600 square feet. I have a thirty pint kenmore dehumidifier that works great.

[teddy bear]

Glad to here you only need a 30 pint dehu. If you a getting the 50-65 cfm of fresh air you should have to purge pollutants and renew oxygen plus moisture generated by 3-4 people, you need 60-80 pints/day of moisture removal. Less fresh air, fewer people, and varing hours of a/c operation provides various levels of humidity. Using residential dehu that removes 30 pints at 80^F, 60% will reduce %RH. Maintaining <50%RH with fresh air and as small a dehu as possible, ok with me. Remember a couple of wet weeks grows mold and dust mites. I must assure our customers <50%RH to avoid condensation under carpets on concrete. I stick with my sizing recommendations of 100 pints per 2,500 sqft. of living area. The crawlspace or basement does not require extra capacity. Been doing this for 15 years with many thousands of installations.

[drk]

Teddy in no way am I saying you are wrong! your suggestion will work! Most people will not won't to spend the extra money. So I recommend on average conditions. If they asked me I would tell them to by a 60 pint dehumidifier. I do not have a HRV or ERV I have a 2.5 yr old so I get a load of unconditioned outside air. It was cool over the week end so I opened the windows NO AC RH was 65% temp this AM was 68 in the house before I left for work I closed the windows and turned my AC and dehumidifier back on. it is now 73 with 55RH does not take long to get it down.

[alota hvac]

I bought a $30 digital hygrometer with Temp & RH Min/Max memory and left it on in the house for 24 hours. The temp range was 72-79^F, the RH range was 51-69%. It's 78^F, 65%RH as I speak at 10:30PM (pretty uncomfortable for sleeping).

TB, will the Heat Pump take out some of that humidity, or are you saying that I still need to take out 100 pints/day on top of that with a dehu? The Sante Fe is about $2300 Canadian tax included (almost US$1900). Should I be waiting until after the HP is installed to see how the RH changed?

As an aside, the various contractors differed in heat load calc methods for the heat pump. The first said based on his experience for this size home, between 3 and 3 1/2 tons, so go with 3 1/2 (very scientific). The second said 1 ton per 800 sf (=3.3 which he rounded up to 3.5). The last used an interesting calculation - follow this one... Take the 1st floor sf (1065) plus half of the 2nd floor (792) = 1857 sf, then estimate 2 tons for the first 1200 sf plus half a ton for each add'l 600 sf. Therefore his estimate for me was 2 1/2 tons, but then he rounded up to 3 tons anyway! I'm totally confused. Based on this, I guess it could be anywhere from 2 1/2 to 3 1/2. Do you recommend the HVAC-Calc software, or should I trust any of these guys?

Thanks again

[alota hvac]

I thought you guys might like my new sig too. I think it's very appropriate!

[teddy bear]

Originally posted by alota hvac

TB, will the Heat Pump take out some of that humidity, or are you saying that I still need to take out 100 pints/day on top of that with a dehu? The Sante Fe is about $2300 Canadian tax included (almost US$1900). Should I be waiting until after the HP is installed to see how the RH changed?
Thanks again
On a hot day with 13 hours of operation, the hp should remove 100 pints of water keeping the home dry. On a rainy day, the dehu may have to remove the 100 pints of moisture. Is the a/c contractor qouting the Santa Fe?

[alota hvac]

They were not mentioning dehus. I asked if they carried the Santa Fe, and one did. He had both a brochure and a price sheet in his binder.

The contractors have been saying that the HP should be sufficient. You've raised my skepticism about HP's capabilities on their own, and your recommendations really make sense to me. Since I can do this in stages, I'll start with the HP, monitor the RH, and then consider the dehu after (gotta wait for another paycheck)!

Thanks.