[Greenbuilding] Insulating old house in zone 4A

[Ross Elliott]

Hi Sacie,

If you are in Ontario, a home energy retrofit rebate program has just been launched that can give you up to $5000 for home energy improvements, including $500 towards a Certified Energy Advisor providing you with a whole-house energy audit and report (other provinces may have their own programs up & running by now as well). Rather than having someone try to diagnose and recommend the best upgrade option from afar, perhaps your best bet is to find a QUALIFIED person in your area who can come out and have a look, then advise you on your best options, and submit the paperwork for your grant when you're done. 

However, it's a sad fact that the previous national retrofit programs brought a few greedy bottom-feeders into the market who hired the lowest paid and least-qualified people possible to do the field work, and this Ontario program has been launched before the new CEA qualifications take effect Jan. 1, 2017, which will hopefully knock some of these spectacularly unqualified people out of the market. Meanwhile, I see some of those old familiar mass-market faces sliding back into this business now that there's money flowing again. There's a simple solution to incompetence though: insist the CEA who provides your energy audit shows proof they have passed both the new NRCan exams - Foundations and Energy Advisor (they've been available for over six months, so there's no excuse for anyone serious about this work not to have taken and passed the exams by now). That doesn't guarantee you're hiring a proper building science expert who really knows about old houses and new materials and techniques, but at least you won't get one of the old blower door monkeys who were only qualified enough to fill in the right checkboxes to get you a government grant. Same advice applies to the rest of Canada, it's not mandatory in all provinces yet to re-train and re-certify as an NRCan CEA, but by January these new exams and qualifications will be Canada-wide.

You say you want to air seal, so the first step is to get a blower door test done that will both quantify your baseline air leakage rate and identify where the air leaks are, then a follow-up air test will show you how much improvement you made.

Insulating and air sealing to the inside has some potential problems, particularly if you don't run continuously through the floor header spaces and interior wall intersections, and remember it has to connect with the continuous ceiling and foundation air barriers or you're wasting your time. Exterior air barrier and continuous insulation is your best (and most expensive) bet. Removing and re-using siding is likely more expensive than all new siding and trim, and certainly a lot more hassle if it's even possible to get it off without wreaking it (please don't put plastic siding on a 134 year old house if you can afford better, so many people slap cheap siding onto old houses and destroy their character, if you retrofit to the exterior please get the trim details right too so it looks like it's original). If you're re-siding anyway then you should add at least 2" of continuous insulation (not polyisocyanurate, perhaps Roxul board or polystyrene). Maybe you might even consider a whole-house deep energy retrofit like Harold Orr's chainsaw retrofit and add Larson trusses with blown cellulose http://www.greenbuildingadvisor.com/blogs/dept/musings/history-chainsaw-retrofit . But to get back to my original advice, I'd suggest teaming up with a local CEA and a good contractor who really knows their stuff, get a blower door test done, and figure out the most cost-effective whole-house approach that gets you the energy savings you want without the pitfalls that come with doing it wrong (the only thing worse than wasting your money is wasting your money on creating a mold farm!).

I assume you have wall cavities that can be insulated with blown-in dense-packed cellulose, or do you have one of those houses like we have around here that were "insulated" with mortar? Properly installed blown-in insulation alone can reduce air leakage substantially.

I also wonder why you feel you need a rainscreen, if the original clapboard is doing fine. And maybe air leakage through the walls is less of an issue than you think, perhaps the basement and attic are the places to start air sealing. But that's why getting an expert on-site might be your best first step to come up with a custom whole-house approach, every house and homeowner's situation is different, and everything you do to your building envelope may have unintended consequences unless you consider the whole package and use the house-as-a-system approach.

An energy audit will also help size your post-retrofit heating system properly, it's likely way over-sized...

Glad to hear you're taking good care of an old house, they're certainly a labour of love, future generations will thank you for doing it right  :-)  

Ross Elliott
Homesol Building Solutions

Message: 1
Date: Sat, 30 Jul 2016 11:23:21 -0500
From: Sacie Lambertson <sacie.lambertson at gmail.com>
To: Greenbuilding <Greenbuilding at lists.bioenergylists.org>
Subject: [Greenbuilding] Insulating old house in zone 4A
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All I really need some good advice here.  We've purchased an old (1883) house in very good shape.  We planned to take off and reuse the exterior siding after we had properly insulated the walls.  But the considerable expense of doing this with the repercussions for the exterior trim, soffit etc has forced us to reconsider our interest in doing this the ideal/best way.

I've done a lot of reading about alternatives but find no conclusive best way to give us a rainscreen behind the existing clapboard behind which is sheathing and the interior.  Nor directions about creating an airtight barrier without taking off the exterior cladding.  We are willing to build slightly to the interior now but since the rooms are not large we don't consider building a full second wall inside the exterior wall.

Of concern: rainscreen, air barrier, air tightness

Good article about rainscreens:
http://www.greenbuildingadvisor.com/blogs/dept/musings/all-about-rainscreens

The following is out of GBA:  Comments?  Better alternatives?

*For health and climate reasons I try to avoid foam. If done right cellulose could work well here I think. A product like Mortairvent, though designed to be used in masonry walls, can be used to create an air gap against siding (or a roof deck in a cathedral ceiling.) It combines a spongy spun polypropylene matrix with an insulweb-like backing and comes in various thicknesses from .25-.80. Seems like it would work just as well with spray foam if it was important to have that larger air gap.*

*And if there are not structural considerations, cross strapping the added interior 2Xs would nearly eliminate thermal bridging.*


Would appreciate advice re best way to handle our situation of properly insulating these walls to the inside.  The rest of the house will be done well, new, well-insulated roof, insulated conditioned crawlspace.  It is the air infiltration issue in the wall assembly that worries me.

thanks, Sacie