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Retrofit / renovation to bring heating costs under control

jca2020 | Posted in Energy Efficiency and Durability on

Hi folks,

Thanks for creating this great resource for newbies like me to learn!

We’re actually near Toronto, Canada, but I think you could consider us Zone 6A for your purposes. We bought our ~2000 ft^2 1981 home last year and suffered a horribly cold and expensive winter, so we’d like to take steps to bring that back in control.

Our house is slab construction, 2 level, no basement, cinder block walls, on first level, and we believe concrete slab flooring for 2nd level, and wood frame, batt-insulated attic. The roof is 45 degree pitched, coming down to ground level and ending about 4ft off the ground, so interior has some sloped walls.

My fear is the slab may be completely uninsulated. The ground-floor windows and sliding door are quite large and original with the 1981 build. Some of them flex considerably to the touch, indicating possibly a loose mounting, or just really thing gauge glass. There are also some ground-floor french doors that were retro-fit, and are poorly insulated. We put in some foam stripping around the sealing surfaces to hopefully help block airflow.

On 2nd floor there are two crawlspaces between the roof and the side walls, each showing batt insulation in the roof rafters, and no insulation on the concrete 2nd floor slab. I believe no insulation on the interior wall to that crawlspace, as I guess they figured the roof was insulated.

Heating is baseboard electric with programmable thermostats in each room (a pain, but bearable). Our largest bill over the winter was approx $750 CAD. In summer, with no active cooling, our bills are $150-$200, for comparison.

We had insulation specialists come in to figure out what to do, but each suggested they’d like to bring in the blown insulation and add some to our attic (for their minimum charge, of course). The lack of creativity and lack of desire to actually measure the home to determine the best course of action was disappointing. One at least suggested getting radiant in-floor heating in our living room to improve comfort, which I would consider, but I also know will not help the ravenous heat loss.

Anyway, long story short, I’m willing to spend some money to improve the situation, but I want that to be spent on the most advantageous jobs to improve comfort/cost.

Any suggestions for how to proceed, or even what type of professional to have come in to actually evaluate? I do have a small thermal camera and have pointed it at everything I can find. There are clearly some insulation defects, but my gut said the problem might be bigger. Maybe I’m wrong and I just need to tear down one piece of drywall at a time until it’s done? I can post pictures (normal and thermal) if you think it would be of help.

Would love to hear any of your thoughts!

Thanks!
Justin

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Justin,
    The standard answer in cases like yours is to have the house evaluated by a certified energy rater (one certified by RESNET or the Building Performance Institute). You can visit the RESNET and BPI websites to search for certified energy raters in your area.

    A good energy rater will show up with a blower door and (if the weather is cold enough) an infrared camera. After your house has been inspected and evaluated, you should be given a customized list of suggested energy retrofit measures, with the most cost-effective measures at the top of the list.

    My guess is that your house needs air sealing work and insulation improvements. In some cases, it may be advisable to consider replacing leaky sliding doors.

    It would probably be cost-effective to abandon your electric-resistance heating system and to rely instead on ductless minisplits.

  2. Expert Member
    Dana Dorsett | | #2

    Don't abandon the electric baseboards, KEEP them- as BACKUP for the mini-splits, since you know they can heat the house.

    A decent mini-split will cut the mid-winter heating bills by more than half, and the entire heating season bill by about 2/3.

    Air sealing and insulating would also likely cut the heating cost by at least a third, so if you really tighten it up and heat with mini-splits your winter bills would be under $350 even for the coldest months.

    Are the cinder block walls insulated at all? How thick is the rafter insulation, and how deep are the rafters?

  3. charlie_sullivan | | #3

    Normally the advice is:
    Step 1) Get an good audit.
    Step 2) Improve the envelope.
    Step 3) With the new envelope, you have a lower heating load, so if you want to consider a new heating system, it becomes cheaper because it's small.

    But with Dana's good advice to keep the electric baseboards, you have the option to install a mini-split cold-climate heat pump sized for the eventual low load, or even sized smaller than that, without worrying much about the sizing. Whatever fraction of the heating it can do is immediate savings, and the rest is still taken care of by the baseboards.

    Unfortunately, your experience with finding the expertise of insulation contractors lacking is not unusual. We could give you advice here on particular issues, but getting a professional auditor sounds well worth it in your case, since there are many open questions.

    A few thoughts on the envelope:
    1) Air sealing is usually a good first step, both because you can get a big benefit from a quick and easy fix when you find the big holes. The blower door test will help you find those. Optionally, you could do some of that yourself first, sealing the obvious leaks, and use the blower door test to find the hidden ones. The energy star web site has a great DIY guide to air sealing.
    2) If the roofing or siding needs to be redone soon anyway, those can be opportunities to add insulation.
    3) For leaky windows and doors, an option is the thin clear plastic film kit you can get at a hardware store to tape over them and then shrink with a hair dryer. You get air sealing and a little insulation benefit, at low cost. The problem is that you have to re-do it each fall if you want to open the windows in the summer, and that gets old fast, but as a temporary fix for this winter while you are figuring out your long-term plan, it can make sense.

  4. wjrobinson | | #4

    You have three great posts of advice. The hard part to swallow is spending money to ... save money, an impossibility. Example... you follow the advice, spend $15,000 on upgrades, and lower your annual costs by $500 or less if you then use more for added comfort. $15,000/$500/year=30 years before savings kicks in. Like all advertising today, "Buy now and save!!" silly humans we are.

    Anyway, good luck, maybe you can air seal for a few dollars and save a few hundred per year, that at least makes cents and actually lowers your costs including the cost to lower your costs...

  5. vensonata | | #5

    Justin, what is your total heating bill for the year? Multiply by 20 and spend 75% of that number on retrofits. Basically, like many people you bought an "unfinished house". It looks finished, but the heating/insulation is simply half done. That is why, usually, the price seems good. But we have to face the finishing costs to get comfort, ecological sanity and economic operation.
    Just as an aside. There is a strange economic consideration with heat pumps. The bigger consumer the house is of heat the better the payback on heat pumps. The investment in the heat pump depends on its total use. A low heat house doesn't payback a 50% reduction in heating which a heat pump will give, but a leaky high heat bill house does. Consider that a passivhaus would be 90% less to heat than yours, a heat pump would save 5% of your heat bill! It is in the shoulder seasons that your heat pump saves you the most since its efficiency is highest in warmer temperatures and your house needs heat, where the superinsulated house doesn't need heat at those times.

  6. wjrobinson | | #6

    Ven, great post as always.

    But let's use numbers now.

    Hvac annual guess $1500*20*.75=$22,950.

    Option 1, sink #22,950 into comfort upgrades.

    Option 2- put $22,950 in an hvac comfort account and pay the Hvac costs monthly from it at a level that provides comfort.

    Comfort both ways and in x years one sells the home and option two left over moneys provides a comfortable trip around the planet....option 1 may help sell the home but assessors don't do comps that way, they look at the market value of that area.

    Option 1 is my choice as it is a job for contractors etc, and is comfort for the customer even though it makes no cents logically. Well emotions add spice to life.

  7. iLikeDirt | | #7

    In order for $22,950 to offset the estimated $1,500/yr heating bill, it would need to provide a stable, average, and safe nominal yearly return of 6.5%. That turns out to be a surprisingly challenging task at a time like this. At a more reasonably-achievable 4%, the sum needed is more like $37,500. Better insulation or equipment makes sense with these kinds of numbers.

  8. Expert Member
    Dana Dorsett | | #8

    The payoff for air sealing and insulating (particularly the CMU walls, if currently not insulated) is as much or more in comfort than net-present-value of future energy savings.

    At Toronto type winter outdoor temps the interior temp of a CMU will be at or below 10C much of the time, even if the air in the house is 20C. If you insulate the walls to at least R10 (R15 would be better) the wall temps would run about 18C in a 20C room. The difference is a dramatically increased average radiation temp within the room, which is something that can be sensed by bare human skin. Most people are more comfortable at 20C air temps with 18C walls than at an 22C air temp with 10C walls.

    The air-leaky low-performance windows & doors ( and other random air leaks of equal or larger magnitude) means the air becomes drier in winter- drier than is optimal for human comfort & health. When you tighten the place up the drafts dissipate, and the moisture content of the air rises. While it's possible (though pretty difficult) to make the place so tight that the moisture could rise TOO much, but that would be a good thing. Retrofitting a modest amount of mechanical ventilation to manage the moisture and other indoor air quality issues isn't necessarily expensive, and it puts the ventilation where it's most appropriate & necessary rather than at random leak points.

  9. jca2020 | | #9

    Thanks for all the tips folks! I'll take the advice to get a blower door / home performance test and see where to go from there. Good points about the payback period and potentially just stashing some money to "pay for comfort" until we move elsewhere.

    Will keep you guys posted. Cheers!

  10. Dana1 | | #10

    FWIW: It's somewhat academic but Toronto's climate is really more like the cold edge of US zone 5A , not 6A The seasonal averages are under 7200 HDD-F / 4000 HDD-C over the past 25 years:

    http://toronto.weatherstats.ca/metrics/hdd.html

    http://www.energyvanguard.com/knowledge/us-climate-zones#table

    This distinction may affect how you insulate some of the assembllies if combining a foam + fiber approach. eg: the amount of exterior foam you would need for dew point control with an unvented roof,

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