Basement Upgrades to Improve Indoor Air Quality
forcedexposure
| Posted in General Questions on
Hello dear GBA folks,
I’m trying to reduce my energy bills and reduce the amount of fossil fuel required to heat and air condition my 1300 sf, 1 1/2 story, 1934 Tudor Rivival house, which is located in the Greater Boston area.
At first, I dreamed of getting to Net Zero. But the cost of that goal exceeded my budget. So, instead, I decided to break up the project into two phases. PHASE ONE of the project includes solar panels, heat pumps, attic and exterior wall and eaves insulation, and air sealing. This PHASE ONE work was budgeted to be recouped in energy savings and incentives over a ten year period.
PHASE ONE work is now complete! The result is that I now have a 9.45 kW PV array, three ductless ASHPs, a tighter (we went from 4050 CFM50 to 2900 CFM50) and better insulated house, smaller energy bills, some debt, and a smelly basement which seems to be contributing to my seasonal asthma.
PHASE TWO of the project was meant to come in a few years from now, after elimating some of the debt from PHASE ONE. PHASE TWO will include tackling the basement. I am not sure exactly what PHASE TWO should involve, beyond adding an ERV, the right kind of insulation, and possibly removing the old gas furnace (as well as the steam radiators throughout the house, which are unbelievably built *into* the exterior walls.
My questions for you good folks are:
1) Can I get by for a few years before starting PHASE TWO, if i keep a dehumidifier running in the basement? Will removing the humidity (and mold) be enough of an air quality improvement?
2) What do you recommend for the PHASE TWO work? Will the basement require vapor barrier treatment to keep the water out? What kind of insulation is best? Will I want a ducted air system for the ERV, to deliver air to the first floor? Will an ERV in the basement reduce radon levels? Will I want a second ERV installed on the second floor, to remove moisture from the bathroom and provide air to the two bedrooms?
Thanks in advance for your consideration and wisdom.
Best Wishes, Kris
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Replies
Do you know your ACH50 number?
If I guess at some numbers I get (2900 x60) /(1400x8)= 15.5 ACH50
If that number is anywhere close your home is abysmal and I have to wonder if you could keep a candle lit on a windy day.
Given how little you blower door number improved it seem they put little effort toward that goal.
My guess if time and effort put toward air sealing the house would pay back in the first year as a DIY project and 6-8 if you paid to get the ACH50 under 2 a Herculean goal given that it has a half story.
I must say the salesman that sold you on solar and heat pumps before air sealing and insulation and left you with a moldy basement are shysters and best avoided before they sell you new windows.
Please take some time and read about air sealing the work in not technical in any way it is hard nasty detailed work that no one will ever see or complement you on but without it you are putting frosting on a turd.
https://www.greenbuildingadvisor.com/article/air-sealing-an-attic
https://www.greenbuildingadvisor.com/question/devils-triangle-update
https://www.greenbuildingadvisor.com/question/devils-triangle-and-cathedral-ceiling-insulation
https://www.greenbuildingadvisor.com/collection/air-barriers-air-sealing
https://www.greenbuildingadvisor.com/article/air-sealing-strategies
https://www.greenbuildingadvisor.com/article/saving-sustainably-air-sealing-and-insulation
Walta
Hi Walta,
Thanks for your reply. I’ll have to calculate the volume of my house and get back to you with an estimated ACH50. The square footage I quoted here doesn’t include the basement space.
I only had really great folks working on my house. The problem was me - I scaled back the recommendations of my awesome contractor and removed the ERV that was planned.
Now I have to deal with that. Maybe I can get an air quality measuring device to help determine how bad the air is.
Best wishes, Kris
+1 on all that. The damp and leaky is the priority here. See lots of discussion on slab moisture (including https://www.greenbuildingadvisor.com/question/seeking-topically-applied-vapor-barrier-for-old-slab-06-perm-rating-class-i )
Hi Walta,
I was able to find the measurements and didn't have to do any estimating:
The air volume in the house is 21090.33 ft³
The house went from 11.69 ACH50 to 8.25 ACH50.
(this is with a wind zone of 2, N-Factor of 16.47, equivalent NACH of .71 before air sealing and insulation, and an effective leakage area of 231.05 in² before air sealing and insulation work).
Please keep in mind that this house has 10 exterior corners, a gable roof, three dormer windows, original windows on the first floor, broken vinyl windows on the second floor.
And the insulation work was way beyond my skillset: In the eaves, five knee walls were cut open in order to insulate the knee wall floors and walls with 2" rigid polyiscuanurate foam, and 16" of cellulose, and also mineral wool batts. The exterior walls of the house received dense-pack cellulose - a tricky job since the house had originally been insulated with mineral wool and the hand-cut shingles had to be carefully cut and reused for patching. The attic received more blown-in cellulose, to get to 16", including in a space inside the gable roof, which really only a mouse could fit into. An insulated "plywood dam" (aka "hatch") was built and installed at the top of the attic stairs to create a better barrier between the unconditioned attic and the 2nd floor bedrooms.
Thanks again for your input. I'll review the links that you've shared and will work on measuring the quality of the air in the house.
best wishes, Kris
IN reply to your original question, a dehumidifier in the basement can help quite a bit. It should either drain by gravity or have a pump to discharge the condensate to a proper drain. You don't want to be emptying buckets. It will use energy and it will warm the basement. This isn't a bad thing in winter but it may be in summer. Still, drying the air is very important.
As far as the best treatment for your basement, spend some time on this site researching. There have been several great articles and untold Q&A threads. You're bound to find some examples of houses similar to yours. In short, fix bulk water leaks first, air leaks second, dampness after that, and don't insulate until you've corrected all three above.
Hi Kris,
The work and your approach to it is smart and admirable. Good on you. As Peter said, there are some helpful articles on the topic of addressing a damp basement. The first that comes to mind is Fixing a Wet Basement. As for your concern about indoor air quality, we are at the start of running a series on the topic, and I think your question about the impact running a dehumidifier on air quality is a good one (and one I am personally interested in, given my basement flooded with river water in the aftermath of Ida last week). I plan to ask one of our HVAC experts to address it in a new post, so stay tuned.