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Community and Q&A

How can I prioritize projects on my 1940s tract house?

kvng | Posted in General Questions on

I’m in the process of closing on a house in Redwood City, CA, climate zone 3, in a FEMA AE Flood Zone. The house is a 1940s, 1000 sqft tract home with shingle siding, 1×3 or 1×4 edit: 1×12 inch plank sheathing, an insulated ceiling with lots of penetrations from can lights, a semi-finished loft that connects garage, attic and living room, a wall furnace for heating, and a recently encapsulated crawlspace.

Things we need to do:
1. Install air-source heat pumps to replace the existing furnace. Given that we’re in a flood zone, I’d like to place these in the attic, which, if I understood, means I should insulate the top or bottom of the roof, though not sure how to apply his advice in a coastal climate with no snow-load.
Things I’d like to do:
1. Install a dedicated ventilation system and/or air seal the house to deal with smoke from the frequent wildfires.
2. Insulate and air-seal the roof, walls, and crawl-space.
3. Remove the old chimney and fireplace that we’re not planning on using and is taking up a good deal of floor and garage space.
4. Maybe finish the remainder of the attic for storage/play space, as #2 is on the way.

Things that we’re interested in avoiding:
1. Smoke infiltration from the increasingly bad fire seasons.
2. Extreme damage from flooding.
3. Poor heating/cooling performance or comfort from the lack of insulation and air-sealing.
4. Structural issues due to the age and construction style of the house.
5. Mildew/Mold in the crawlspace contributing to poor air quality.
6. Fire danger because of the lack of fire-resistant siding.

Note on 4: The inspection pointed out that some collar ties had been removed, there was a “normal amount of sagging for a roof of this age and structure,” and there’s a long, horizontal crack in the perimeter foundation of the exterior wall of the garage (you could get a dime inside it, but maybe not a quarter).

Note on 5: The crawlspace was “sealed” by the previous owner and they installed a sump-pump, but I haven’t been able to check if they sealed the vents and it doesn’t look like there’s any insulation. There’s still some mold down there, but it could be that the company didn’t remediate it properly. Also, given that I’m in a flood zone, would it make sense to install an insulated flood-vent product like

I don’t have a complete picture on the state of any of these issues because I only have limited access to the house at the moment, but if there’s something you think would help answer any of my questions, please let me know and I’ll try to figure it out next time I’m able to go over there.

– First, is this a nightmare, or am I blowing this out of proportion? I’m a semi-informed consumer with no professional building experience and too many podcasts under my belt, so I don’t know if these are standard issues that can be ignored or addressed on a reasonable budget, or if I’m buying a money-pit.
– Second, what should I prioritize? I don’t have the time or money to do a gut renovation, which probably makes air-sealing and insulation complicated. Are there ways around that? Do I take the siding off and put on exterior insulation? Rebuild the roof so I can condition the attic and put up something more substantial than 2×4 rafters? Finish conditioning the crawlspace (they appear to have only put in a CleanSpace liner)? Ignore all of this and get a thicker jacket and an ice-maker?
– Third, how do I find people I can trust to do this work with and for me? I’ve talked to plenty of techs that seem confused by my questions and concerns. Am I overthinking things? Are these considerations not important in the Bay Area, which historically has a really mild climate and no snow? (I’ve been trying to use but people are either hard to get a hold of or have backlogs of work. Also, super jealous of Palo Alto, which is subsidizing performance audits almost entirely).

Sorry if that’s a lot. Not really sure where to go from here.

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  1. Expert Member
    BILL WICHERS | | #1

    Looks like you have a lot of things to do here :-)

    I would deal with any structural issues first. Structural issues are the biggest safety issue to deal with, and they're also usually one of, if not the most distruptive repair work you can do. Do this work first, then worry about everything else. Be careful with your planning so that you can minimize rework too -- if you have to open up a wall for a structural repair, insulate that wall before you close it back up.

    I would look into air sealing and insulating next. You can clean up any mold you find at the same time, since you'll be working in the areas mold could be while you're doing the insulating work. Exactly how you insulate something depends on how the place is built and where the area being insulated is within a home (wall, roof, ceiling, floor, below-grade wall, etc.). It's difficult to give you any useful info about how to go about insulating without knowing a lot more about your structure. Note that you don't have to insulate EVERYTHING at once -- you can insulate as you go, doing the project in phases. Some things you should try to do together (don't just insulate half of your attic, for example), but others can be easily split up (walls in different rooms, for example). If you're going to be doing a reside, replacing your siding, that's a great time to add insulation to exterior walls. Depending on your wall construction, I'd try to use mineral wool batts and then at least enough exterior rigid foam for your climate zone. This avoids the need to be concerned with vapor retarders on the interior, and is sometimes easier from an air sealing perspective as well as potentially being less disruptive (it's often easier to pull of siding than to pull down interior drywall or plaster, for example).

    Have that chimney inspected. If it's dangerous, put it into the "Structural" repair timeline and do it first. You don't want it falling on you. If it's safe but taking up space, I'd just check to be sure the damper in the flue seals well and then leave any demolition work until it lines up with a project in that same area of the house.

    If you have an encapsulated crawl space, you can put your HVAC equipment down there. If you put it in the attic, you want to seal the attic and bring it inside the building envelope to avoid performance issues. I would try to keep it out of the attic if at all possible. Are floods enough of an issue to really be concerned about that? Would water levels get high enough often enough for this to be a real concern?

    Flood vents might be a code requirement. They're a good idea regardless. Their purpose is in part to minimize the potential for structural damage in case of a flood.

    Finding contractors you can trust is a trick. There ARE good contractors out there. Most good contractors will be involved in forums like this so that they can keep up on new stuff in their trades. Finding the first reliable contractor can be a challenge, but once you have someone you like (quality work, honest, fair prices, willing to work with you), ask THAT contractor to recommend OTHER contractors for other trades you need. Once you find that first reliable contractor, you can usually find others with referrals from the first.

    You'll get a lot of other good ideas on there, and I recommend reading some of the articles too. You'll find a lot of good info that will help you to do things right.

    BTW, if you are worried about smoke, you want to keep your house a slight positive pressure with respect to the outdoors, and you want a combination of a fine particulate filter (MERV 13, etc.) in front of an activated carbon filter. You NEED that particulate filter to keep the activate carbon filter from clogging quickly, but the activated carbon filter is the one that will get out a lot of the smells and other things too small for even the very fine particulate filters to get. Positive pressure can be provided by some HRV systems, or just use a fan, like a duct booster fan. It doesn't usually take very much if it's running all the time.


  2. kvng | | #2

    Thanks for the detailed and thoughtful answer Bill. The point about locating the hvac in the crawlspace makes sense, and is appealing if we want to finish the whole attic.

    The other question I'd have is, is it worth re-siding the house because we want to insulate? The shingles look great and they seem to be performing well, but we've already been turned down for a home insurance quote due to the fire risk.

    Also, there's a closet they added by attaching a cantilevered bump-out. Are those considered standard or sensible? I was kinda taken aback when I saw it.

  3. Expert Member
    BILL WICHERS | | #3

    Residing may well be worth doing if you want to insulate, especially if you have NO insulation now. Insulating from the outside is WAY less disruptive to the interior, and you can easily added continuous (exterior rigid foam) insulation which, if thick enough for your climate zone, eliminates the need for interior vapor retarders. You also can air seal with those exterior walls open. If you don't have a lot of interior renovation to do, residing is often the easier option for adding insulation if you don't want to do something fancy with one of the "fill a closed wall" types of insulation. If your siding is in rough shape, then it's pretty much a no-brainer to insulate from the outside.

    If you've been turned down for insurance, then that's another thing to push you towards insulating from the exterior. You can also make sure you have all your detailing optimized for a fire zone this way. I don't ever have to deal with the fire issues in your area, but I know there are some special vents and building methods to minimize risk. You can also use fire resistant exterior materials like fiber cement siding.

    I'd look closely at that bump-out. If it was done DIY, you could potentially have foundation issues around it and mold/rot of the wood structure there. You CAN build such a bump out to last, but they're often prone to problems. If you will be opening up your exterior for new siding anyway, that would be a good time to check that bump out to see if anything needs work.


  4. kvng | | #4

    Thanks again Bill; all good ideas. My big takeaways and extrapolations from your comments are as follows, so correct me if I missed anything or came to the wrong conclusion:
    1. Get a structural engineer to look at the place soon, and try to correct anything dramatic before we move in or before we do any significant work on the place. Priorities in order: foundation, roof, chimney, and probably that bump-out.
    2. Residing and installing exterior insulation + air sealing is probably the best way to get insulation and air-sealing done on the walls of the house, especially because we can get away with not disturbing the interior finishes, blowing in difficult-to-remove foam, or rotting the existing sheathing.
    3. The roof cladding is also apparently nearing the end of its useful lifespan. Re-roofing could also be another opportunity to apply rigid foam insulation and an air/vapor control layer to the roof without needing to permanently adhere something like spray foam on the interior of the structure. It also presents an opportunity extend the overhangs on the gable end of the house, as those are a bit wimpy.
    4. HVAC in the crawlspace, while attractive and probably a good idea, also might not be code-compliant because of the section referenced in the attached image. That said, it's a lot easier to have the crawlspace insulated and sealed before we move in, where the roof+attic might take more time *and* be made more difficult by sticking ducts up there.
    5. The combination of filters and a dedicated fan sound like the way to go with the smoke concerns, but was that a dedicated system or inline with the heating and cooling? MERV 13 would also cover concerns with allergens, which would keep the Mrs. very happy.

  5. Expert Member
    BILL WICHERS | | #5

    For #3, you could add rigid foam on top of the roof, but you could also (depending on the depth of the rafters and a few other things), work "backwards" and build a vented roof from the outside. You'd basically put in batts, then rigid foam, then leave a ventilation gap (1" minimum), then new sheathing. If you have shallow rafters that can't accommodate enough insulation for your climate zone, then you'd be better off completely filling the rafter bays with batts and putting enough rigid foam on top of the sheathing to get you up to code minimum for your climate zone. You have to make sure you also have the correct ratio of rigid to fluffy for your climate zone if you go this route -- you can't safely add an extra R5 on top to get to R38 (for example), because R5 isn't enough for dew point control when the other R33 is interior batts.

    For #4, if you have any doubts regarding placement of the HVAC equipment in your region, call your local building department and ask them. This should be a pretty easy question for them to answer, and they'll know what is necessary in your specific location.

    For #5, HVAC and the positive pressure system would be different. An HVAC system ideally just recirculates air in the house and doesn't create either a positive or negative pressure differential with respect to the outdoors. Makeup air would be handled by exterior ventilation. Sometimes this is an HRV, but as I mentioned, if you just want a slight positive pressure, you can use a small blower and filter housing. Systems made for this purpose exist for commercial systems, but I'm not aware of one for a residential system. That doesn't mean such a system doesn't exist -- it's just that I work more in the commercial world so I'm more familiar with the equipment used in those settings.


  6. walta100 | | #6

    I am sorry to be a dream crusher but it will cost way too much money to turn this sow’s ear into a silk purse.

    All 40s houses are post war material were in short supply and housing was in very high demand. Almost everything was built as small as possible less than 1000 sqf no time or materials for charm and details just fast and simple. A fireplace would have been a big luxury option. With that said it is hard to believe this is your forever dream home. It is your starter home or home for the next few years and that is great but you need to recognize that as a fact. If you decide to make changes to the house they must add to the resale value of the home.

    I think it is foolish to spend big money on this or any other house that is in the 500 year floodplain.

    Why is the furnace on the must replace list? Is it broken beyond repair? Will this add to the resale value not unless the old unit is useless?

    Opening up the walls and adding insulation will not add one penny to the resale value and will take 100 year to repay the cost at today’s fuel prices.

    Short of stripping every wall down to the studs it is very very unlikely you will be able to stop enough of the air leaks to make a ventilation system necessary or effective.

    Adding insulation does not add to the resale value of a home it can be a good investment only if you stay in the home long enough to recover the cost in fuel savings. Given today’s fuel prices wall insulation will never see a payback and if the attic floor has any more than R8 add to that will have a very long payback.

    Removing the fire place detracts from the homes resale value. The floor space you could recover will not change the number of square feet on the real estate paperwork and that is the number that adds value to the sale.

    Adding or bring a staircase up to code in these tiny houses very often destroys the floor plan and looks awkward.

    You need to understand the TV shows about real estate are total fiction. If you pay a contractor to make home improvements you will never recover more than 100% of the costs at resale. DIY it is possible if you do very good work, buy at the right price and in the right neighborhoods.

    I say enjoy this house for what it is and save your money to build your dream home.


  7. kvng | | #7

    Thanks Walta, and don't worry, I'm also here for this kind of skeptical analysis.

    I will say that my expectation isn't that I'll recover a ton of value from anything we're discussing here; my ambition is almost entirely to improve the comfort of the house. That said, if it's more a question of the original structure being too low-quality, as you mentioned with the air-sealing and ventilation, then it makes sense to not throw good money after bad. The heartening thing about Bill's comments is that I could choose to tackle a lot of these projects after moving in, without needing to displace everything I own or the whole family. By then I should also have a clearer idea about the comfort of the home.

    Removing the wall heater makes sense to me because the existing unit doesn't actually heat the whole house. The previous owners had to use a number of space heaters to make up the difference. So if I do install a heat pump, that'll be a significant increase in the livability of the home, especially as the summers here get hotter and hotter.

    Having spoken with my realtor, it doesn't sound like the chimneys are a big draw for homes in the area, and he didn't expect removing it to impact the home value at all. The house is already small, so freeing up a wall in the living room and space in the garage for storage feels like a good idea. That said, I could be wrong and maybe the average buyer still finds them attractive in a way I just don't.

  8. Expert Member
    Dana Dorsett | | #8

    In order of priority structural first, air sealing second, insulation is third. Dense-packing old plank sheathed walls does a lot for air sealing, but not nearly as much as a fully-adhered weather barrier.

    Laying down a heavy polyethylene or HPDM ground vapor barrier and air sealing the crawlspace walls does a lot for for reducing stack effect infiltration. IRC code requires either a prescribed minimum of crawlspace ventilation or a dehumidifier to manage crawl space moisture. (CA code may differ- I haven't chased that down in Title 24 recently.) In fire-hazard country take the dehumidifer approach.

    Chimneys are nothing but a liability if you're going to be heating with a heat pump (or even with condensing propane.) Good call on just getting rid of it.

    Use the fuel use from last winter to get a handle on the design heat load for specifying the heat pump. It can be a bit tricky to get good accuracy in zone 3 unless measuring it only during cold snap events- seasonal or even monthly fuel use is all over the place due to insufficient heating degree-days, or having cooling degree days even during the heating season. But the methodology for that lives here:

    Otherwise, run free Manual-J-ish online tools such as CoolCalc or LoadCalc, and be sure to NOT upsize from those results, which are typically padded. Be sure to assume effectively zero infiltration & ventilation using those tools, which can really blow up the oversize factor unnecessarily for houses that have undergone a decent round of air sealing.

  9. walta100 | | #9

    Remind me what are you saving? The roof, no the siding, no the HVAC, no, the electrical and plumbing systems, the 70 year old windows?

    It seems impossible that people lived in a house with inadequate heat for 70 plus years. If you said adding AC was a must have I would stop arguing the point.

    Realtor’s are total yes men and will never say anything that might discourage any potential buyer. I will stop believing in fireplace value when they take it off the spec sheets.


    1. Expert Member
      Dana Dorsett | | #10

      >"I will stop believing in fireplace value when they take it off the spec sheets."

      Fireplaces are big air leaks that allow (and sometimes drive) way too much outdoor air infiltration, which violates one of the primary design goals:

      >"1. Install a dedicated ventilation system and/or air seal the house to deal with smoke from the frequent wildfires."

      To re-build it to a perfectly seal-able chimney only for some unspecified uptick in resale value doesn't seem like money well spent, and leaving it as-is just isn't an option.

      Getting rid of ALL combustion appliances (not just the open hearth fireplace) is also a worthwhile measure in wildfire-prone areas. If it's dry enough for the woods & brush to burn easily the wood of the building is also dry enough to ignite more easily, and not having a fuel tank or gas line on the property also reduces fire risk.

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