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Community and Q&A

Suggestion for making a 30 year old home more efficient while roof and siding are off

bren77 | Posted in Energy Efficiency and Durability on

We live in Columbus, Ohio and have a home built in 1986 with the following floors. Floorplans and photo are attached as an FYI.
– Basement: 740sf finished, 250sf crawl space
– 1st floor: 1000sf
– 2nd floor: 800sf

We have siding (90%) and brick (10%) exterior. We plan to replace the roof (including sheeting), siding, and doors soon along with many other updates including replacing the wood burning fireplace with a direct vent and replacing all of the fans in our bathrooms. The windows are vinyl, double pain — we plan to keep them. We have central air with a gas furnace and AC that are both about 12 years old. We have a radon system in the basement.

While the exterior of our home (roof, walls) is exposed we would like to make some changes to our home to make it more energy efficient. I found the article on this site very helpful: I realize we can’t do anything that extensive, but hope to be able to make our house much more efficient and green than it currently is.

I would really appreciate your advice regarding the items below and/or any other suggestions you have that are not too expensive.

Some things we are considering and related questions:
1. Replacing our existing furnace and AC with a ductless minisplit with three lines (one unity for each floor). Would a unit on each floor be sufficient?
2. Replacing the insulation in our walls while the siding is off? What type is best? I was planning on using Tyvek over the insulation until I started reading some things on your site. Sounds like that is a bad idea. Is there something else we should wrap the house in before putting the siding on?
3. Replacing the insulation in our attic while the roof is off. What kind should we use?
4. What type of patio door should we look for?
5. What type of entry door should we look for?
6. If our house is better sealed, I’m wondering about the air quality and considering HRV, ERV, or standard fans in the bathrooms to improve airflow.
7. Is there anything else you’d recommend?


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  1. iLikeDirt | | #1

    Out of curiosity, why are you planning on replacing the siding, roofing and especially the roof sheathing? From your picture, the shingles look to be in pretty good condition, and they're some of the nicer ones too. The siding looks fine too. Is there some hidden damage that's not visible in the picture?

    Honestly the three most cost-effective things you can do are things that don't require removing and replacing the siding and roofing at all: air sealing, and attic floor insulation, and basement wall insulation.

    If it was me who was was preparing to pump some cash into that house, I would knock down the interior walls separating the kitchen, dining room, and living room, and turn it into one nice big room. You'd get back a lot of space currently wasted on that weird L-shaped entry foyer. Then I would put a wood-burning insert into the useless fireplace.

  2. bren77 | | #2

    Nathaniel, thank you.

    Good questions. We are replacing the siding and roofing because we have a hail damage claim. We are replacing the sheathing because we have mold in the attic above our 2nd story.

    Can you give more details about what you mean by "air sealing" and "basement wall insulation"? We're planning on attic insulation but we're not sure which kind is best.

    We are planning on knocking out the wall between the kitchen and dining room. I believe the wall between the living room and kitchen is load bearing.

    Thanks again.

  3. iLikeDirt | | #3

    In that case, my priority #1 would be to replace the damaged materials with ones that can't be hail-damaged in the future. That would be a heavy gauge metal roof and brick siding, or maybe fiber cement. Spend your and the insurance company's money on more durable things that won't need future replacement rather than higher insurance premiums.

    If you have mold in the attic, you absolutely need to determine what caused it rather than just replacing the damaged materials without addressing the root cause.

    As for air sealing and basement wall insulation, I would suggest reading through this; the linked pages will answer all of your questions:

    To get back to your original question, the things you can to to improve your house's energy efficiency while the roof and siding are off would be the following:

    1. Add 3-6" of foam insulation boards over the wall sheathing, and build out the window boxes and door fames with new metal or PVC jamb extensions to accommodate the extra thickness
    2. Use sheathing with a radiant barrier on the underside as your new roof sheathing
    3. Use a light-colored or bare metal roof instead of shingles

    Seriously though, air sealing, attic floor, and basement wall insulation (particularly the rim joists) will probably be more cost-effective.

  4. GBA Editor
    Martin Holladay | | #4

    Q. "Can you give more details about what you mean by 'air sealing' and 'basement wall insulation'?"

    A. These issues are fundamental, and it's essential that you understand them before you decide how to proceed with your renovations.

    For more information on air sealing, see these articles:

    Questions and Answers About Air Barriers

    Air Sealing an Attic

    Air-Sealing a Basement

    For information on basement insulation, see this article: How to Insulate a Basement Wall.

    For information on energy improvements to an existing house, see Energy Upgrades for Beginners.

    For information on adding insulation to walls when the siding is off, see How to Install Rigid Foam Sheathing.

  5. BobHr | | #5

    How much of the sheathing is being replaced. Is it all the sheathing or a few sheats. If all the sheathing is being replaced I would use the type with the attached radiant barrier. It would be on of the few time I would use a radiant barrier as is should only be a small increase.

    The mold is likely caused by air leaks from the house to the attic. Air ceiling the attic floor would be of great benefit both from an energy conservation, comfort and mold prevention.

    Proper attic ventilation would be the next step. DO NOT install a powered attic fan. When venting the attic there should be a baffle in every rafter bay. Guys take short cuts and you will likely find that every 3rd or 4th bay has a baffle.

    BAthroom fans are another area I see done improperly. Given the age of your house there is a good chance the bathroom fans are vented into the attic. Bath fans should be vented through the roof.

    I favor cellulose insulation in the attic. It can top off the existing insulation.

    The walls are a little more complicated without knowing what your budget is and what is planned on the siding replacement. I am guessing you might have a 1/2 in rigid insulation under the siding. If they can remove the siding without destroying the rigid insulation then I would look at air sealing the existing insulation and the adding a 2nd layer and air sealing it also.

    Thermal imaging the walls prior to the work would give you an idea if the cavity insulation is up to par.

  6. Expert Member
    Dana Dorsett | | #6

    "1. Replacing our existing furnace and AC with a ductless minisplit with three lines (one unity for each floor). Would a unit on each floor be sufficient?"

    Looking at your floor plans, unless you're going to replace the windows too (to lower the individual room loads) you'd be looking at a mini-ducted version for each of the above grade floors, which would require figuring out where to route the ducts. The basement zone might be do-able with a single head, or if insulated may not even need that. This might be better to do with the smallest-available 3-zone multi-split and one compressor. The individual room loads and whole floor/zone loads would have to be calculated to figure out what works best.

    If you have a mid to late winter fuel bill, a ZIP code (for weather data purposes) and the exact meter reading dates and fuel use between readings, it's possible to derive an upper bound on the whole house, but it wouldn't tell us much about the individual room loads.

    "2. Replacing the insulation in our walls while the siding is off? What type is best? I was planning on using Tyvek over the insulation until I started reading some things on your site. Sounds like that is a bad idea. Is there something else we should wrap the house in before putting the siding on?"

    There is nothing wrong with using housewrap under the new siding detailing it as an air barrier. Detailing the sheathing itself as the primary air barrier would be a more reliable air-barrier.

    It's possible to correct any cavity insulation voids & compressions with blown fiber insulation installed from the exterior, but it takes a blower door & infra-red imaging test to find them. Find a weatherization/insulation contractor who uses those techniques.

    Before you put the new siding on, verify if there is/isn't an interior side vapor barrier (foil facers on batts, or polyethylene film.) If there is no vapor barrier and it's 2x4 construction, you probably have sufficient space to add 1" of foil faced polyiso (nominally R6, derates to ~R5.5s in this application & climate) on the exterior of your sheathing & housewrap, which will cut your wall losses by about 35% what they would be with just cavity-insulation. If you go that route it's worth using a crinkle type housewrap (eg Tyvek DrainWrap), taking care that the window flashing is lapped correctly to the housewrap. Tack the polyiso in place with cap-nails, and seal the seams with a temperature-rated high quality aluminum tape (eg Nashua 324a ). Rip some 1/2" OSB to 2" wide strips through-nailed to the studs a each stud, and hang the new siding on the OSB using ring shank nails short enough to not fully pass through the foam. That adds about 1.5" to the total wall thickness.

    If it's 2x6 studs you'll have to go to 1.5" polyiso for dew point control, which adds 2" to the wall thickness. That may or may not be do-able.

    If you have to go thinner than that with the exterior insulation or if there is an interior side vapor barrier like foil or polyethylene, use rigid rock wool instead of foam. (Roxul ComfortBoard or similar.)

    "3. Replacing the insulation in our attic while the roof is off. What kind should we use?"

    If there is sufficient space between the attic floor and roof deck at the eaves to install 14-15" of blown cellulose with an inch of clearance to the roof deck, that would be the cheapest way to bring it up to IRC 2012 code-min. But that's not very likely. Insulating at the roof deck is substantially more expensive, but if your rafters are 2x8 you could install R28-R30 high density fiberglass or rock wool batts tight to the roof deck, and 4" of polyiso above the roof deck and have sufficient dew-point control to protect the roof deck from interior side moisture drives.

    If they're only 2x6 rafters, R23 rock wool between the rafters + 4" of exterior side foam isn't quite code min from an R-value point of view, but may be sufficient on a U-factor basis (which would require detailed calculation based on the exact framing, since it would be close.)

    If you insulate at the roof deck it's fine to leave the attic floor insulation in place. It's still doing you SOME good, but you're not allowed to count it's R value toward the code-minimums. IN an extreme case it might become a roof-deck dew point issue, but if you installed a smart vapor retarder under the rafter insulation (you can do it for less than $200 of additional material cost) any potential problems are safely averted.

    "4. What type of patio door should we look for?"

    Swinging patio doors have more reliable weatherstripping than sliders. Insulated patio doors with only partial glass tend to have lower/better overall U-factors than mostly-glass versions.

    "5. What type of entry door should we look for?"

    Insulated fiberglass or steel doors with a U-factor of 0.25 or less are available.

    "6. If our house is better sealed, I'm wondering about the air quality and considering HRV, ERV, or standard fans in the bathrooms to improve airflow."

    Air sealing typically improves overall air quality as long as you get religious about the use of exhaust ventilation in the kitchen & bath. If using heat recovery ventilation to allow higher ventilation rates without much energy-use penalty, your climate there's some rationale for ERV over HRV, but either works just fine. On the humid-days of summer ventilating with an ERV would inject slightly less latent cooling load than an HRV, but you could also just dial back the ventilation rates when the outdoor dew points are north of 65F.

    "7. Is there anything else you'd recommend?

    Check to see how the brick faced section of the house is doing. Ideally it would have weep-holes every third brick or so at the bottom course, and either open venting at the top behind the existing siding, or vent holes every third brick or so along the top course so that when the brick heats up it convects air behind the brick, purging the moist air, replacing it with drier outdoor air. Brick takes on dew/rain moisture, and releases it with intense bursts when heated by the sun. Properly venting the space between the brick & sheathing goes a long way toward avoiding potential moisture problems in the studwall behind it.

    There may be huge air leaks and little or no insulation behind your wood-sided chimney, depending on how it's constructed. Those issues may be resolvable once the siding is removed. Details of what (if anything) you can do there will vary with the actual construction. The fireplace itself is probably a huge heat leak, not just the chase where it's installed. An air-tight woodburning insert can be a solution to some of the fireplace air leakage issues, and also becomes a reasonably efficient auxilliary soure of heat, provided there is reasonable insulation between the chimney and the great outdoors.

  7. Expert Member
    Dana Dorsett | | #7

    Correcting myself...

    It occurs to me that rigid rock wool doesn't come in low thicknesses, thus if for geometry reasons you have to go less than 1" for exterior foam it's best to use UNFACED rigid EPS foam, which is sufficiently vapor permeable to allow reasonable drying rates, but will still provide some thermal break over the framing, and keep the sheathing warmer (=drier), for higher moisture resilience. Even 1/2" EPS reduces the heat loss of 2x4 framing by a significant fraction.

  8. bren77 | | #8

    THANK YOU ALL for this very helpful information. I need to read through your responses more thoroughly, watch the videos, etc, but I wanted to say that I really appreciate the very thorough responses. This will be a tremendous help with our plans.

  9. bren77 | | #9

    Thank you again for your great input. We are a few days away from starting our project and I need to make some final decisions regarding materials. I hope the very knowledgeable individuals who commented are able to see this and respond...

    We plan to remove the soffits and replace them with vinyl to greatly improve airflow and increase the gaps at the ridges.
    A. We plan to replace the sheathing on our 2nd story roof. It sounds like most/all of you think including a radiant barrier is a good idea, correct? I've read some articles that say otherwise.
    B. We have about 12" of fiberglass insulation in 2nd story attic. We will probably blow in some more on top. Any recommendations?
    C. Our 1st story roof is over our garage and family room. We don't There is very little insulation over the garage in the attic. Should we add insulation there even though it is unconditioned space?
    D. We plan to use standard asphalt shingles that aren't black but are pretty dark in color. I know this isn't ideal, but I don't think metal would be an option for us or the roofers. Is there anything we should look for with the shingles besides picking a color that is as light as possible?

    E. We plan to use rigid foam on the exterior with a radiant barrier on both sides. The contractor recommended just 3/8" but it sounds like you all are recommending more like 1", correct? (we live in Zone 5) Is the radiant barrier a good idea? I think that 1" is probably the max we can do for cost and hassle with the windows not being changed. Any suggestions on specific brand/type or installation?
    F. I believe the existing walls are fiberglass batt and rigid foam with no moisture barrier. We plan to do a visual check and fill any gaps with batt and foam before installed the rigid foam layer (described above). Do we need a blower door test to do this well? Other suggestions?
    G. We aren't currently planning on using a Tyvek (or similar) house wrap under the rigid foam. Is that a good/bad idea?

    Thanks again!

  10. GBA Editor
    Martin Holladay | | #10

    Your plan to install 1 inch of rigid foam on the exterior side of your walls will only work (a) if your walls are framed with 2x4s, and (b) if you choose a type of rigid foam that with an R-value of R-5 or above.

    If your walls are framed with 2x6s, you'll need to use rigid foam rated at R-7.5 or more. For more information on this topic, see Calculating the Minimum Thickness of Rigid Foam Sheathing.

    If you have to replace some of your roof sheathing, replacing the old sheathing with radiant-barrier sheathing is OK (but not essential). The radiant barrier may lower your air conditioning bills slightly -- although if your attic has an adequate level of insulation, the radiant barrier won't do much. (However, if you are in the unfortunate position of having ducts in the attic, the radiant barrier is probably a good idea.)

    The radiant barrier may increase your heating bills during the winter, but not by much.

  11. GBA Editor
    Martin Holladay | | #11

    Q. "We aren't currently planning on using a Tyvek (or similar) house wrap under the rigid foam. Is that a good/bad idea?"

    A. Every wall need a water-resistive barrier (WRB). It is required by building codes and recommended by experts. You can use rigid foam as your WRB if you want, but doing so is tricky, and there are many limitations when you use this approach. Remember, all of your window flashing has to be integrated with your WRB. That's usually easier to do when you use plastic housewrap (for example, Tyvek or Typar) rather than rigid foam as your WRB.

    Whatever method you use, you have to know which layer is acting as your WRB -- or else your flashing details will become chaotic.

    For more information on this topic, see:

    All About Water-Resistive Barriers

    Where Does the Housewrap Go?

  12. bren77 | | #12

    Martin, thank you for your replies.

    Few clarifications for others who may post:
    - we have 2x4 walls
    - no ducts in the attic
    - In light of Martin's advice, I think we will use Tyvek (or the Lowes equivalent) as our WRB.
    - I will look for R-5+ rigid foam

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