Home retrofit project
Poot_Klopp
| Posted in General Questions on
Hello all,
I’m looking at the final plan for a home retrofit in zone 5. I had a few contractors bid and they all essentially came up with the same recommendations shown in the picture attached. The company I picked is highly reviewed, state certified (qualifies me for the state rebate and financing) and completed an in depth audit (thermal imaging, blower door, etc). I wanted to get some final peace of mind before committing to the project. Any input would be appreciated. This is on a 1920s built home with balloon framing (more on that below). As such I’m really just looking to make things better without introducing new problems.
2 crawl spaces
– Everything here seems straightforward
Attic
– Again straightforward
– Rafter baffles are also being added
Walls
– Every company had the same recommendation of blown in dense pack from the exterior.
– We are planning on updating the siding in the future, but for now that is not in the budget. Future plans would hopefully include going down to the original sheathing and adding a well sealed zip system below new siding and maybe some exterior insulation.
– Currently we have vinyl siding, 1″ EPS (I’ve been told that was used to help level vinyl), original wood siding, tar paper, original board sheathing. No interior cavity insulation.
– We have no leaks or water issues
Rim joist
– Straightforward
Areas of concern
Wall assembly
– Vapor control, could the recommended solution above cause moisture problems?
Rim joist
– Spray foam: Is it safe? I still don’t know the brand they plan to use, waiting to hear about that.
– Also worried about how they plan to seal the balloon frame opening in the basement.
– Should I be concerned with electrical wires running along the rim that may get covered?
– What else am I forgetting about?
I know this is a lot of info and each area has 100’s of articles posted, but not being an expert makes digesting all that information difficult. I don’t expect to have a perfect envelope or perfect r values, I’m looking to make the home better than it is now but not any worse. The projected energy savings are 29%. I’d appreciate any input and feedback on the project.
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Replies
Buildings of this vintage are some of the best retrofit candidates around. Vinyl siding makes dense pack cellulose easy. And 30% is a reasonable improvement. That's a pretty high blower door number so you might do a bit better depending.
A few suggestions:
--any wiring upgrades should be done now because it will be much harder later. And you can't assume you don't have knob and tube wiring even if you don't see it in the basement--lots of times I find a vestigial circuit here or there.
-make sure to air seal interior wall top plates carefully before insulating the attic. Sometimes they are wide open or semi-open into the attic.
-sometimes balloon cavities have a bypass into the soffits just under the top plate. If you don't want the soffits full of cellulose, those gaps in the wall can be stuffed with rockwool or something. It's an painfully awkward job though.
-be careful with plumbing on exterior walls. If water pipes currently rely on heat loss to avoid freezing, then insulating can cause pipes to burst.
Dense pack cellulose should be just fine. If the installers are competent and they get proper density, there shouldn't be any or moisture issues. Only thing to watch for is a wall that can't dry either in or out--vinyl wall paper on the inside and masonry on the outside or something like that.
Re spray foam. Well, many of us don't like the health implications especially flame retardants, so it's good to minimize the use of it. But honestly there isn't really an effective alternative for rim joists. The formulas seem to have gotten better, but you still hear the occasional horror story about a job gone bad. Seems like less than 1% but still. The wires can be covered, just makes life hard for future electricians.
Assuming you have attic ventilation? Also pay attention to air sealing around the attic hatch. Should have a gasket or something. If it's a pull down stair, that can be difficult.
After the project you might want to monitor humidity in the crawl spaces and basement if there is one and install a dehumidifier if necessary.
Good luck with it. You'll have a heat pump-ready house when you're done.
Norm,
Thank you so much for the response. I really appreciate it. I had a walkthrough with the on site manager today, he was very knowledgeable and thorough regarding the scope of work. He discussed mostly everything you mentioned! I'll be sure to have them check for soffit issues when they are installing the baffles. No knob and tube thankfully, I have rewired almost every switch and outlet in the home. We have no plumbing on exterior walls. The attic hatch is on the list to be insulated and air sealed. We currently have a dehumidifier running, I will keep an eye on humidity levels. The spray foam is unfortunate but I'm feeling better about it after doing dinner more research. It will only be used on the rim joist and the we discussed heavily ventilating the basement. Thank you again for the input.
The plan sounds great maybe too good to be true.
The sceptic in me says 1020s story and half house with a blower door test of 1.24 ACH50 before any work is not plausible. 12.4 would be a number one might expect and 22.4 could be believable.
The idea that a 1920s house is likely to get air sealed down to .35 ACH50 is laughable at best and deceptive and fraudulent if they can say it with a straight face. 0.35 ACH50 is 50% below passive house standard and a great feat if achieved in new construction.
What is the current attic insulation level?
Is the projected energy savings are 29% written in the contract or anywhere else?
Walta
Pretty sure that the ACH in that report is ACH natural and not ACH50.
Walta, I'm not sure about the ach. The savings calculation was based on insulation and air sealing. As far as I know, that number is used to qualify me for the state rebate and financing I got. My guess is having no wall insulation and very little attic is what helps the most. The attic was calculated around r18 currently. I'm not expecting to have an air tight home and I don't think they gave me a specific target number, only that it will be better.
To unpack what Walta said about the impossible blower door score in that report:
They claim that the blower door measured 5600 CFM50. Multiply that by 60 to get 336000 CFH50 (cubic feet per HOUR at 50 pascals).
If the 1.24 ACH50 is to be believed, it implies that the house's volume is 336000CFH50/1.24 ACH50 = 270967 cubic feet. That is the volume of a cube 64 feet on each side. I suspect that the house isn't 6 stories high.
If, as Walta suggests, they misplaced a decimal point, the calculated volume would be 336000/12.4 = 27096 cubic feet. That's a cube 30 feet on each side, which sounds much more realistic.
The report didn't mention your square footage, but I suspect it's between 2000 and 3000, which would make sense with the 12.4 ACH50 number.
I also second Walta's assertion that 0.35 ACH50 is a ludicrous claim to make (and pointless to attempt to achieve). Perhaps it was also a case of a misplaced decimal point and they meant 3.5ACH50, which is a pretty good improvement and also very achievable.
That all makes sense, the conversions and what not was kinda hard for me to wrap my head around. You did a great job breaking it down. The primary 1st/2nd floor is a little over 1500sq ft. with 9ft ceilings. The basement would bring it to the 2500sq ft. number. Not sure if the attic and basement would need to be included in the total cubic ft calculation. They did not say they were expecting the house to reach those numbers, just that those numbers are the "recommended" standard. The work is scheduled to start tomorrow. Let's see what happens!
My old house scored 15 ACH50. If I get even close to 1 ACH50 when we're done I'll be thrilled.