Purest possible residential HVAC setup for new home for child

Go with the Trane Clean Effects. Obviously her health is important to you so you will set aside the time to regularly clean the thing, unlike most people. When it is clean it is the most efficient in the industry, the only problem is people who actually keep theirs clean are the minority. Also go with a variable speed blower and 2 stage condenser. This will keep the air moving over that filter for long periods of time, so you get more filtered air.

In addition, Trane claims their electronic one doesn't produce ozone.

Thread relocated to AOP

I would consider first a ventilating whole house dehumidifier. In a new home, indoor pollutants from new, modern materails may cause more issues than jsut dust and pollen. A dehumidifier and ventilation will dilute these and keep indoor humidiy in an ideal range which is improtant for someone with sensitive lungs and airway. In many ways a new construction home might be a lot workse than an 80+ year old home with original flooring and more natural materials in terms of indoor pollutants. It actually easier to mitigate things like lead paint and asbestos than the off-gassing for synthetic modern materials for those that are ultra sensitive.

For reducing dust, a good vacuum cleaner used 2-3 times a week with a HEPA filter with be 10X more effective than anything other than a commericial clean room air handler.

Keeping the home under slightly positive pressure will make a big difference.

A MERV 13 Media filter will pull out plenty of allergens as 1/4 the cost of an actual HEPA filter.

One more recommendation. Get ride of all carpeting if you have any. Tile or real hardwood is more sanitary, doesn't contribute to airborn dust and contains fewer chemicals overall.



A litlte off topic... but if I was building a custom home for someone that was ultra sensitive, I've actually specifiy a completely ICF home with tile floors and beleive it or not, plaster walls (antimicrobial and no dust during installation) with radiant heat, zoned chiller water cooling with hot water reheat and steam humidification, and a whole house ventilation system with continous exhaust in bathroom and the kitchen. The garage would be mostly detached and completely sealed. Plus a cool roof design with a conditoned attic with closed cell insualtion under the roof. Window area would be at least 25% using larger picture windows since they are tighter and you don't need an many operable windows in this design.

A lot of good stuff has already been posted above. All I will add is that if you want to assure the cleanest air via filtration possible, you need to constantly circulate and filter this air. Standalone filtration units where your daughter spends a lot of time may be a way to assure filtration continues when the HVAC system is not running. These units are available with carbon filters (which will give you gas phase filtration). The challenge of putting high levels of filtration in HVAC equipment is doing so without causing an excessive pressure drop through the system. That is, if the filters are too restrictive, the HVAC will not funtion properly, and can be damaged over time as well.

I also can't stress highly enough how important quality source control is, as others above have mentioned. Don't put stinky stuff in your house. No formaldehydes, minimal VOC paints and other materials as much as possible. And you will need to be vigilant about this...it can sneak in many ways that on the surface appear innocuous. You don't want to build an ultra airtight house only to seal in a bunch of toxic, stinky stuff. Basic rule of thumb on construction material VOC content is that if it has a strong odor, it's probably toxic. In practical terms that means no wallpaper, no oil based primers or paints on the millwork, no formaldehydes in the insulation or in the cabinets and shelving material, etc. Also be choosy about floor coverings and window treatments. And furniture. The stinky stuff can sneak in multiple ways.

Here are my thoughts on what I would do if I was in your situation.
First, I would highly seal the home or use spray foam insulation to KEEP OUT all possible issues
Second you will NEED an HRV or some sort of fresh air ventilation
Third Radiant floor system or Daikin Quaternity(the quaternity might be to much for your size house)
If you do not go radiant or ductless make sure your ducts are sealed as good as they can be, 6% or less is good 3% or less is possible and we routinely are able to seal our duct systems to a 3% duct loss on a brand new home. Any ductwork that you can keep inside the envelope is a good thing, open web joists or conditioned attic areas for the trunk lines.
The Trane clean effects is a great product, but you need to clean in monthly or more often for best performance. The Carrier unit is the same as the Honeywell truClean and the truclean may cost a bit less so you might want to look into that but as others have said they are expensive for replacement filters. A HEPA filtration system is also a great option if you want very very low ozone emissions but a HEPA system costs about 3X as much as tru clean filters in my experience.
Lastly, you might also want to look into some of the new plumbing pipe options. I recently had a customer use a type of plumbing that had no VOC emisions and it was fused together.
Look at no or zero VOC paint and finish's and have an air test performed once the house is operational via an Air Advice or similar unit to verify that everything is as clean as stated.

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Originally Posted by motoguy128

Keeping the home under slightly positive pressure will make a big difference.

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Originally Posted by Shophound

constantly circulate and filter this air. .

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Originally Posted by SkyHeating

highly seal the home or use spray foam insulation to KEEP OUT all possible issues
Second you will NEED an HRV or some sort of fresh air ventilation

make sure your ducts are sealed as good as they can be, 6% or less is good 3% or less is possible and we routinely are able to seal our duct systems to a 3% duct loss on a brand new home. Any ductwork that you can keep inside the envelope is a good thing, open web joists or conditioned attic areas for the trunk lines.

have an air test performed once the house is operational via an Air Advice or similar unit to verify that everything is as clean as stated.

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Manage RH to stay between 40-50% rh. Avoid dust/static on one side and mold on the other.

I wonder if you could actually find a plasterer anymore. I would be cool to see a new home done in plaster. 0 dust when installing plaster. Again line based plaster is antimicrobial too. Its' installed wet and cures without any VOC's. Drywall is a absolute mess... and thats an understatement.

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Originally Posted by SkyHeating

Third Radiant floor system or Daikin Quaternity(the quaternity might be to much for your size house)

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you mean Daikin Altherma?

Quaternity is their fancy ductless splits, The Altherma system is the one that does hydro heat + AC.

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Originally Posted by mark beiser

you mean Daikin Altherma?

Quaternity is their fancy ductless splits, The Altherma system is the one that does hydro heat + AC.

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No I mean the Quaternity, it has built in flash streamers and air purification. Plus since it does not have any ducts it won't allow any duct leakage and with up to 22 SEER and 15.8 EER and 11 HSPF it is incredibly efficient. It can also control humidity with dehumidification on demand in high humidity areas. It is a ductless meant specifically for air quality and I have used it with many customers with moderate allergies or humidity concerns with great success.
It just really is not the right solution for a large home and can only be used in a 1 outdoor to 1 indoor unit combination. You can not use the Quaternity indoor wall port with any of the multi port ductless.

See post 13 from Solar Mike. Good advice.
And # 9 from amd.
What he is saying is - your forced air HVAC system cannot clean the air. That is not it's design or porpoise.

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Originally Posted by biglew

My daughter has very bad allergies and a very weak immune system

We are building a new house and we are entirely focused on creating as clean an environment as possible for her (no carpets, no rugs, etc).

Clearly a whole house HEPA filter seems to be the way to go - what we would like your opinon on is are other add-ons like charcol filters, UV lamps (Non ozone), gas phase filters, etc that will improve upon a whole house HEPA.

If i could create a clean room at home i would, but that costs hundreds of thousands - we are comfortable spending up to $30k - $50k on the HVAC equipment for a our 4,000 sq foot house (not including duct work etc) to make it the best environment for her as possible

Thank you in advance - all advice is much appreciated

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L O C A T I O N ?

uneedlocalengineertoaddressyourspecificneeds!

Start with one or two UltraAire HEPA units depending on residence in either AZ or MS or Puerto Rico or Calgary.
http://www.thermastor.com/Ultra-Aire-XT155H/

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Originally Posted by biglew

My daughter has very bad allergies and a very weak immune system

We are building a new house and we are entirely focused on creating as clean an environment as possible ...
Clearly a whole house HEPA filter seems to be the way to go - what we would like your opinon on is are other add-ons like ...

If i could create a clean room at home i would, but that costs hundreds of thousands - we are comfortable spending
up to $30k - $50k on the HVAC equipment for a our 4,000 sq foot house (not including duct work etc) to make it the best environment for her as possible

all advice is much appreciated

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CONCENTRATE ON the Building ENVELOPE and the HVAC equipment size/costs decreases signficantly !