Plan to address IAQ
I'm hoping the experts here can help me lay out a plan for addressing IAQ of my Houston home.
I have a 4200sq ft 2-story home (2010 build) with 2 Carrier Infinity 2-stage systems and Infinity controls. Downstairs has 4 zones, upstairs has 1 zone. There is a fresh air inlet on the downstairs system. Filtering is currently achieved with 1" filters on each of the returns.
I want to add serious filtering to the system because of my wife's severe allergies and I want to add supplemental dehimidification because the system can't hit dehumidification target of 50% (Infinity T-stat is reading 60% but is set for comfort at 50%).
What testing / steps should I take to get the proper equipment installed? Blower door test for leakage, duct leakage testing, etc?
The house was built in 2010 but is not super-efficient. The blower is in the unconditioned attic and all runs are flexible ducting. The roof has techshield but is not conditioned and there is no spray foam. The builder used expanding foam (can style) on most of the exterior framing joints, but it's not a true spray-foam installation. The exterior walls all have normal pink insulation installed.
Windows are double paned low-e glass, but in the winter months I regularly get water buildup on the windows. I also can feel some air blowing past window sills.
The 2 primary drivers are the humidity level (houston is notorious for mold) and my wife's allergies.
We are in a bit of a unique situation in that we are not currently living in the house so we have about a year to do the research, planning, and testing before we move back in.
I'm thinking I need to do the following:
Blower door test to measure the house leakage - mainly to check if leakage is too high and address if necessary, but also to see if I even need any actual "fresh-air" intake on the main system.
Duct test to measure the duct leakage - address as necessary / possible
Install whole-house dehumidifier (April-aire or similar) and connect the existing fresh air inlet to this unit instead of the downstairs air handler (assume the fan would run on some sort of duty cycle with the de-humidification kicking in when necessary?) Any way to control this with the Infinity system?
Install some sort of allergen filter (carbon, thick pleated, electronic?)
I'd love to be able to install equipment that can be controlled by the existing Infinity controls, but it's not a necessity.
Sorry for all the details but I don't know much about filtration and humidity control and the contractors I've worked with here in Houston have been terrible to say the least. Even the Carrier rep was clueless about my Infinity system.
Thanks in advance for the discussion!
We can go into many directions and some answers may be helpful. But the way i would approach this house is to get a engineer to survey your house and make recommendations. perform an air balance etc..
With all the info you gave us you don't give us the size of the AC units. There are many factors that we would need to know, Duct size-supply and return, Model#, age. How are the unit running now. any issues. past or present. A really good PM would be the first thing i get so i have those results for the engineer.
Also, How are the controls working? Find an HVAC vendor who knows both systems, If they don't know, don't hire them.
The systems Re both 4-ton and are working great. I have no complaints at all with the carrier system aside from not getting humidity below 50%. The units run about 70% of the time in low stage.
I really am looking for info on what steps to take to address the general indoor air quality. I have been reading like crazy and it seems like a certified energy audit is the first step and then going from there. Should I also get an air and particle analysis done? Any other testing that should be done?
I understand the general idea is to have a fresh air change every 3-4 hours when the house is occupied, preferably with filtered air, and to keep the humidity between 30-50%. Here in Houston the humidity is the hardest problem.
I guess I'm just wondering what the most reasonable approach is for a 2-story 2-unit household of 4200sq ft? Electric air cleaner in each furnace, separate whole house filter/dehumidifier, carbon filters, thick pleated filters? Just not sure what's the latest and greatest equipment /technology these days without completely breaking the bank :)
My suggestion if cost is not a concern: Add an independent duct whole house hepa/VOC air cleaner (such as Airpura 600W series) which can recirculate and clean air constantly regardless of whether the HVAC is running and, if money is no object, add an ERV which feeds the outdoor air into the return line of the air cleaner for distribution into the home. Forget trying to use the HVAC system to clean air or add fresh air. For the HVAC system, just add a highly rated 4 or 5 inch filter box, such as the Lennox Merv 16/ Merv 10 or the Honeywell Merv 14 system. If you are in a very humid area, could consider adding a ventilating dehumidifier to bring fresh (dry) air into the home instead of the ERV.
Well the allergy problem... you can always try a Micro power Guard electronic Filter, and Oxy Quantum UV light system w/ an 0-3 generator which only puts out 0.5 PPM .....I have bad allergy problems and I'm telling you it works!!
Unfortunately cost is a concern ;) I don't mind spending some money for good IAQ but I can't just write a blank check :)
If my calculations are correct, my 4200 sq ft home with 10 and 9 ft ceilings will require ~220cfm of fresh air intake to change the air once every 3 hours. Assuming I can seal off the home as much as possible, most of that 220cfm will need to come from a fresh air intake system. I doubt that the existing fresh air intake is capable of bringing in that much fresh air. I think it makes a lot of sense to install a whole-house filtration / dehydration system sized appropriately for fresh air intake.
Thanks for the recommendations, I'll research the Airpura and micro power guard systems.
you should hire an energy rater.
blower door test the house, test the ductwork prior to any
work being done. (once work is completed re-test..and if you
this way you know where you are now and what your target is
going into the project.
verification of work is to assure you that what you paid for was
once you know how tight the house is..and how much duct leakage
you have,a target for sealing will be provided.
your rater will be able to show you leakage areas & give you
guidence as to how to seal these areas.
depending on where the leakage is, you'll address in order of
importance. attic to living space leaks first.
these will include any recessed lights that aren't air tight,
oversized cuts at stove vents, bath fans, supply boxes & return
openings into the attic allow attic temps along with insulation
particles & voc's into the house..the air barrier between attic &
living space needs to be as perfect as possible.
any thermal bypasses..fireplace boxing open to attic, openings from
attic into living space will also need to be sealed..then insulated.
ducts mastic sealed, not foil or duct tape, but mastic & mastic tape only.
no great suff foam for duct or returns. none, mastic only. make that a requirement.
once ducts and returns are sealed..install a 4" media filter.
condensation on windows is probably from high relative humidity.
in my/your/our hot humid climate target RH% is 50%. realistically 30% isn't going
to be easy to achieve..or even worthwhile. once house/ducts are sealed then
less outdoor high RH air will be entering. 50% RH will be comfortable & tstat
settings will be higher as air will be colder & drier.
then to add a whole house dehumidifier would be the next step.
I have an april aire dehumidifier. these units can be set up to
add fresh air to the house. Teddy Bear is the guy you'd want to talk
with here about these units. his help was invaluable in helping me
to determine the best set up for my unit.
I think you'll find that you'll need less than 220 cfm of fresh air, but
ashrae 62.2 ventiation strategy will determine that amount. to get these
numbers you'll need the blower door test to determine air changes per hour
that your house has. there is a bit more to it that adding air!
start with an energy rater that has existing home & allergy experience.
you need to know where your house is...where you want to improve it..
and what those improvements achieve. then you determine the method
of dehumidification, fresh air & better iaq.
and have them verify the installs, and the performance of the installs.
I see lots of people spend a lot of money on uv lights, crazy expensive filtration
systems & never solve anything.
without considering the whole of the house
instead of different parts of it..you won't get the solutions you desire.
check with resnet for an accredited experienced energy rater in your area.
they should be able to recommend companies they have worked sucessfully
with on other projects.
you'll want an experienced installer for the whole
house dehumidifier & people who understand what air/duct sealing actually
quite a bit of the work can be diy if you chose. if you plan to hire someone
to do the air sealing..you should have them on site to 'see' the leakage areas
so that they understand what is to be achieved.
you can do a LOT with a couple of cases of caulk & mastic to lower air &
at the bottom of the page you can search for a rater in your area.
talk with several & describe your concerns to each. ask how long they
have been in the business & for refrences of people with similar issues
find someone you are comfortable with that will take time to
explain & actually show you the air leakage sites, rather than someone
just telling you how much leakage the house/ducts have.
best of luck.