Improving Wall Insulation in Existing Home 5a
Hello, this is my first post here, and have read only a handful of posts. I am looking for some ideas and assistance with improving the envelope of my home. Sorry if the post seems wordy, or if my ideas are incorrect. Feel free to correct me if I am wrong.
I live in a standard 2 story home, built in the 60s in the upper midwest, climate zone 5a. The home is 2×4 construction, and we have made some updates in the 10 years we have lived here, all before we were introduced to green building techniques, energy efficiency, and the idea of a passive house. We have perfomed the following upgrades.
1. Installation of Geothermal heating and cooling.
2. Replacement of windows to 2 pane high E windows.
3. Replacement of worn siding with Hardyboard cement siding.
4. Additional blown in insulation in the attic, with sealing around penetrating fixtures.
Because of these items, it doesn’t make sense to do a full passive house renovation. However, I would like to greatly improve the insulation of the exterior walls. The item I am really attempting not to do is removing the siding and starting from scratch.
The idea that I have would be to re-insulate the house from the interior. My biggest concern is: When they took off the old siding to put on the new siding, they didn’t add a vapor barrier to the back side of the siding. they just attached it to the existing sheathing. Which was the standard fiberous sheathing they used in the 60s. This means I essentially do not have an external vapor barrier.
So with that, what I was thinking of doing was adding a second interior wall in front of the existing one. My process would include stripping and gutting all of the existing sheetrock and insulation (mostly unfaced fiberglass) reinsulating with a better insulation. Then add a second 2×4 or other wall in front of the existing wall into the inside, and insulating that. However, this is about when I get stuck.
Here are the questions I have:
1. After I remove the insulation, can I install a vapor barrier on the external side of the wall cavity? This would go on the back side of the fiberous sheathing that was used when the house was constructed.
2. What should this layered insulation look like?
3. Are there any items I should take into consideration?
I realize all of the electrical and HVAC would have to move into the interior walls, which seem like an easier task than to remove the siding and insulate from the exterior. I also realize that the size of the interior will essentially get smaller. which I am okay with.
Thanks for reading my post and thank you for your replies.
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Replies
Do you know what if anything is currently in your walls?
The truth is passive house standard has no dollars sign in the equation and almost never makes economic sense.
If you have anything in your wall upgrading is very unlikely to make economic sense.
Generally, in your zone one would not install a vapor barrier on the exterior but one would expect a water barrier behind the siding often a house wrap.
Did the new siding get installed over the original siding or was it removed?
If your walls are empty cellulose can be blowen in from either the interior or exterior. From the interior it will be messy and patching the drywall often requires a repaint and will be invisible. From the exterior the holes get plugged and will be visible. The walls need to have an exterior water barrier and painted drywall is enough of an interior vapor barrier.
This money may be better spent buying enough solar to run the heat pump instead of reducing the heat load.
Walta
Thanks for your reply, great questions. Currently in the wall is just fiberglass bat insulation, standard R11 stuff from the 1960s. I am not making this decision based on economics entirely, I realize that it will cost a fair amount of money, and it will not have an ROI. I am making the decision based on comfort and the desire to lower my own carbon/energy usage footprint. I actually do have solar, but didn't think of mentioning it, as it doesn't really pertain.
When the siding was installed, I do not remember them putting a moisture or water barrier on the house, which I did think was odd at the time, but I didn't know any better. They did remove the old siding to put up the new siding. It was the LP siding that had the class action against it because it would chip off chunks of it in the freezing temperatures.
No matter what you do to the existing walls, even using the most effective R6.5/inch insulations, youre still only going to get an R20, which would be better, but I would like to shoot for closer to R30.
Other reasoning for this project idea is that humidity is uncontrollable. With no vapor barrier, and no moisture barrier, the humidity is always high >55% even with a whole home dehumidifier running practically all the time. This obviously changes to the opposite in the winter, with low humidity values, and subsequently dry skin.
I understand that this project wouldn't be what a lot of people choose, and I wish I had understood things better before I had the siding and windows replaced. However, at this time, it's pretty much do something drastic, or move. With being a bit house poor, and liking where we live, I would prefer to stay.
Again, thanks for your comment, and if you have any other ideas, do let me know.
Unless you live in a desert 55% summer time humidity is as good as is possible without over cooling and reheating almost never done short of a museum.
To my ear it sounds like you need to focus your efforts in creating an affective air barrier.
Have you had a blower door test?
Walta
Good question. Yes I did have a blower door test done. The result was 2575 cfm50 at 2628 sqft. (must be external square footage, I wish I had that much square footage) which from a quick google translates to about 7.8 ACH50 which is not "good." This is something that I would like to tackle at the same time. As most of the penetrations and gaps would be easier to see when the walls are bare. Also, correct me if I am wrong, an air barrier would go on the between the drywall and the insulation, so I would be removing the drywall anyway.
When I mention the humidity, I say 55% is the absolute lowest it gets on a dry day on a moderate summer day ~65% outside with the dehimidifier running 24/7. The other day when it was 90% humidity outside, I didn't see anything lower than 70% in the house, so it is indeed a problem.
When tackling these problems, my thought process is that if I am opening up the walls to improve these issues including the humidity issue and air barrier, that increasing the insulation amount would be a good thing to do at the same time.
I appreciate your questions, as it gives me a good ability to clarify some of my thoughts.
The location of the air barrier is irrelevant. Inside, outside or in the center does not matter multiple barriers is fine all that matters is that you stop the flow.
It is not complex work just dirty and tedious. You could duct tape a few box fans in the windows to repressurize the house. Then use the smoke from incense sticks and a bright light to locate the leaks and plug them. Without the fancy blower door gages you will not know how much difference you have made.
Yes 7 ACH50is bad.
Is it possible your cooling equipment is oversized? What percentage of the time is it running on the hottest days?
Is the fan set to auto or continuous?
Walta
The geothermal system is not oversized for the home. I made sure of that. The routing of the duct work is not the best (some upstairs runs go up the outside walls). I have a different project in mind to fix some of that and to make that more efficient. The runtime on the hottest days is 8hrs or 1/3rd of the time, but I also keep it at 74°F. The fan is on continuously during the night time to get the upstairs to match the downstairs more consistently. It is in auto during the day, since I work fromt he room the thermostat is in. The fan runs when the dehumidifier is running. There are a lot of penetrations in the ceilings into the vented attic where I think a lot of the largest problems are, but I think in general the house is leaky.
It sounds to me like you don't think that adding additional insulation would be beneficial, which I can respect. I do understand that the thicker you go the less return you get. However reading newer energy recommendations, R19 is suggested minimum for wall insulation in my zone. The 2x4 construction of the wall can only reach R13 with standard insulation.
My thoughts were to reach that R19 at a minimum. To do this there are a couple of ways that I see as options. First is to add 2x2s to each stud and reinsulate as a 2x6 wall, this will give me 5 inches of capable insulation enough to get to R20 with an insulation like rockwool at R4/inch. The cost of 2x2s is nearly the equivalent of 2x4s unless you purchase 2x4's and rip each one of them.
My process would be to forgo ripping each 2x4 and just install the 2x4s this gives 7 inch cavity for insulation, or R30 rockwool comfortbatt with a 1/2inch offset.
From our conversation, I think the process would look like this:
1. Remove current sheetrock and insulation
2. Add an interior 2x4 wall.
3. Move inward electrical and HVAC.
4. Reinsulate with appropriate insulation (leaning towards rockwool).
5. Install an air/vapor barrier. Along with addressing any other penetration concerns.
6. Sheetrock and trim
Where I still get confused, and maybe I am reading the wrong things online is, since there is no house wrap/moisture barrier under the siding aside from the original sheathing, is there something that I could or should do for the most outside layer of insulation?
I have looked into other options, such as adding insulation like open cell sprayfoam/ blown in cellulose to improve the current situation, but those companies want to go in from the exterior which would be cutting holes into the existing siding. Going through the interior is also an option, but the cost was almost the same as gutting and reinsulating, but would only reach R13 instead of R16. They also dont address areas like rim joists and the first to second floor cantileaver.
I did plan on addressing the air barrier during this project, but after our conversation, and additional reading, I think I will take better care in the process of air sealing. I will also look into products that could get a better seal to get my ACH50 number down.
Again, thanks for your questions and responses. I have a better understanding. I know that you would probably do things differently, and I respect that. However, overall, does this remodel sound ill-conceived? Aside from putting more emphasis on a proper air barrier, that is.
We all have a point of view and motivations and yes, I am all about the dollars. I can respect that you may have different goals. Please take a moment and think about what your goal really is and if it is to be paid member of the passive house club that is cool.
From an economic point of view this upgrade does not make sense.
From a green point of view removing reasonably useable insulation, drywall, trim and paint and sending it to the landfill decades early while requiring it replacement to be mined manufactured and shipped early is ungreen for a marginal reduction in fuel usage seems silly to me but that is me.
To my ear the only thing this wall upgrade gets you is bragging rights that my wall has X R value.
Seems to me a correctly sized AC equipment would operate nearly 100% of the time when at the design temp.
Walta
Here is what I would do with your exterior walls (former spray & injected foam contractor) - I am doing this as part of a deep energy retrofit ...
Strip siding
Take off sheathing
Remove fiberglass
Cut zip R sheathing in half into 2' X 8' strips
Install zip R sheathing horizontally
Inject "slow-rise" polyurethane foam into wall cavity in 2' lifts
Use an infrared camera from inside to make sure you have gotten all voids (expanding/curing foam is an exothermic reaction)
Apply ventilated rainscreen
Apply hardiboard siding
Done!
R-30 wall that is thermally broken & air tight!
Plus you don't have to relocate the wiring - not a trivial task.
OA,
What you are proposing is usually called a Deep-Energy Retrofit. If you use the GBA search function you will see that they aren't very popular among experts because they a) don't ever end up paying for themselves, and b) use more carbon than they save over time.
The low hanging fruit for your house would be to do extensive air-sealing, and introduce mechanical ventilation, which should both save a lot of energy, and improve both indoor air quality and humility levels.
That said, people have different motivations , and if you decide for other reasons to go ahead I would suggest:
- Treat the walls as they do in this article to limit bulk water intrusion from the outside: https://www.greenbuildingadvisor.com/article/managing-water-and-insulating-walls-without-sheathing
- Consider limiting the additional wall insulation to 1 1/2" interior foam board. This will mean less space is lost to new framed walls, less disruption of the existing electrical services, and a relatively good increase in R-value, while still allowing you to do air-sealing, etc. and hang the new drywall with0ut strapping.
I would get someone in with a blower door and thermal camera before deciding to do anything. We're in zone 4a and did a pretty extensive energy retrofit two years ago. We concentrated on the rim joist, the ceiling, and thermally separating the garage from the livable space. Most of our exterior walls are uninsulated double block so around r3. We left the walls alone. We did before and after blower door which went from ach10+(couldn't fully pressurize) to ach3. The house is so much more comfortable as a result. We still have two rooms with vaulted ceilings and one floor on piers that we didn't fix too.