Air quality improvements, hopefully with energy savings
Good Afternoon,
My name is Jimmy Criswell and I live in Midlothian Texas (Climate Zone 3 – about 15 miles south of Dallas). I live in a 1984 ranch style 1450 square foot home with a hip roof with a low pitch. It actually has 2 hips because the garage is on the side of the house where you can faintly see the truck. I only have about 4″ between the exterior top plate and the roof sheathing.
House has kraft faced R11 fiberglass batts on all exterior walls and R-44 fiberglass in the ceiling. We have recently had a bad case of rodent activity which I have corrected. I now have to go through and get all 20″ of insulation removed due to the mice droppings and urine. My house currently has only 8′ ceilings. I have some money set aside but am a single income family and may have to do this in stages so helping me with priorities would be appreciated as well.
I am looking for advice on how to approach my problems.
1. I am debating on a proper strategy as I have air sealed some of the attic but nothing else in the house. How should I approach the removal and reinstall of insulation since it will be done diy and I have to de-sanitize as I go. The room with 2 exterior walls is about 5 degrees colder than the other rooms in the house this time of year. I am willing to remove drywall to increase R value of exterior walls as well as airseal. Recommendations? I have thought about polyiso and batts.
2. We will be installing new central air heat pump at the beginning of March. I am looking for ways to get the ducts inside as air handler is in closet but supply plenum and ducts are in attic but am on hold from removing insulation to re-insulate due to current weather (cold) and the lack of a strategy. Our home will get toasty hot while the electric heat runs for just a short few minutes but then gets cold again rather quickly resulting in short cycling. I am not sure it runs all day even in the few 110 degree days we get throughout the summer and probably only then does it properly de-humidfy. Currently a 3 ton 13 seer unmatched unit with 2007 outdoor unit and original air handler which I am pretty sure is oversized.
3.I am going to have a difficult time creating an airtight air barrier due to the lack of workable height in the attic where the eaves are met. What is the best strategy to deal with this? What type of insulation and where should it be placed? Currently have soffit vents (not enought) and 2 ridge vents. One for the house and another partitioned hip over the attached garage.
I would like to know what order to pursue these problems in as indoor air quality and comfort are my 2 largest concerns. We are either hot or freezing all the time. Any help would be appreciated. Windows were replaced in 2016 with dual pane argon filled low e 366 glass.
I am very handy and can complete much of this on my own. My uncle is in hvac and can help me upgrade the hvac system and ducts though I am considering raised soffits above the attic floor to semi condition the ductwork. I am working on a budget of about 12,000 and believe I can do a 16 seer carrier for about $4-5,000.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Hi Jimmy -
You are asking all the right questions. On the broadest of levels, I worked on each of your major numbered questions:
1. air sealing - really important to get this right because of the energy, moisture, and indoor air quality impact of getting air sealing done right. I would recommend you use the Energy Star Thermal Bypass checklist as your guide (https://www.greenbuildingadvisor.com/detail-library/building-plans-for-the-energy-star-thermal-bypass-checklist) to start and then:
Before I had a blower door, I would use one or more powerful window box fans to depressurize my house or spaces and then use the back of my hand or a smokestack to ferret out the air leaks.
2. ducts in conditioned space - YES, and again from both an energy and IAQ perspective, this is a good move. When you spec your new HVAC equipment, make are that you have a sensible heat ratio (SHR) of no more than 0.70; and lower is better so that in addition to right-sizing the unit for best moisture removal, you also have a unit designed/configured for more latent load management.
3. In my opinion, if you have to choose between getting the air control layer continuous and venting (although not exactly sure why it would be competitive between the two...), go with time and effort on air sealing--you can't vent your way out of a moisture problem resulting from air leakage. Again, the Thermal Bypass Checklist and guidance by fan pressure to find the leaks can really help you get a better air barrier.
What do you recommend for exterior wall insulation replacement or addition? I currently have R-11 Kraft Faced Owens Corning. Thinking about adding some time of rigid foam on studs and then new drywall.
Regarding attic...it is cold right now and I cannot remove my insulation all at once. The strategy I am considering...due to the rodent feces, is to work one section at a time. I will remove insulation, clean and disinfect, then replace insulation highest value batts I can find in the joist bays, and add blown in after project is complete including HVAC system in March. Does rigid foam have a place in this type of install to minimize height and still achieve R49?
I intend to build inverted soffit to cover hvac when project is complete and would like to have a narrow walkway to access equipment for maintenance and equipment checks.
Any ideas would be appreciated!