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Hello from the SF Bay Area

Hi all!

Very interested to hear perspectives from folks living in or working on renovated older homes in Mediterranean climates. And also from "experimentalist" types — if you've instrumented your home to measure its performance, you know who you are ...

With my wife and two kids, I've just bought a 100-year-old fixer-upper in the lovely East Bay (San Francisco Bay Area). I'm trained as an ambient air quality scientist, by the way, but this is my first home.

Among my primary concerns is the fact that it was previously owned (and lived in for ~40 years) by a smoker. Now, if I didn't think this could be handled, I wouldn't have bought the house. The third-hand smoke is concentrated, thankfully, in one or two rooms (and not the bedrooms). But i'm interested in ideas, and empirically tested techniques — both for my own home and for the large amount of SF Bay Area housing stock that's similarly burdened.

Apart from that specific issue, I suppose the IAQ + RHT issues would be pretty minimal. I expect the house now gets about, oh, maybe 50 ACH_50% hr-1. :-) I'm in favor of going combustion-free (e.g. heat pumps) but I don't know what combinations of approaches, in this mild climate, make the most sense for domestic hot water + heat + ventilation (no active A/C required). I'm still hoping to find more relevant case studies to learn from, whether that's through Google or through forums like this one!

Questions welcome anytime. Thanks for the time & attention to read this post.

All the best,


  • Terry PortierTerry Portier Posts: 19
    edited April 15
    Welcome. I'm from So Cal myself. Although nice weather, I never thought of it as a "Mediterranean" climate. I use to surf the entire coast line from Steamers Lane Santa-Cruz to the tip of Baja in my youth.

    "I'm trained as an ambient air quality scientist".

    Now that's an interesting title I never heard of. Assuming it falls under Environmental Science or Engineering? I'm glad this site is attracting more subject matter experts like this...

    Building's process lots of ambient air most don't understand including ones that develop standards. The industry, especially DIYs, one offs, now seals homes down to below 1 ACH w/o knowing nor following standards to test IAQ/OAQ for intake locations. for example, Last I checked EPA does not give the entire nation an A OAQ air quality grade. Despite filtration, some could be lowering IAQ or causing materials to degrade. I see lots of acid/salt rot in CA along the coast, for example, or CO, that may not be good to process through buildings, and cannot be filtered.

    "But i'm interested in ideas, and empirically tested techniques.."

    The best place for general minimum empirical data/requirements is local building code, but it will lack proper reference to air quality. This industry cannot afford proper testing of sorts at the product level and especially the building level nor is it managed properly. There are some Building Computer Models that can based on limited instrumented lab and field test but, they are expensive and have long learning curves.

    CA is the most advanced I'd venture to say in many areas of high performance with bragging rights to boot, it can also be the most ridiculous money making bureaucracy too. Don't know it you seen this. Time will tell if this bankrupts builders or drives the cost of homes even higher to ridiculous levels they already are. Perhaps not as difficut as cold climates, but I don't think CA has it's IAQ/OAQ worked out better than anyone else.


    I'm currently doing consulting work in a lab conducting several test. There we use simulated or conditioned ambient air in chambers depending on climate requirements driven by international standards. Feel free to chime in. I'll be doing Acidic Atmosphere, Fungi, Corrosion, soon.

    Test Thread: http://archive.homeenergypros.org/discussion/11516/hot-box-testing#latest

    This IOT thread discusses a new 2020 era of connecting hardware (instrumentation, etc) to interconnected software's....

    I consult Aero/Auto outside AEC too, where there is plenty of $$$ for such validations/empirical data, not found here, nor on forums or blogs. For the most part, you will however find plenty of "ideas" some good, some bad, not backed by testing or life cycle management, other than perhaps personal opinions or visual inspections that can be misleading. I'm hoping this site is the first to at least change that by its professional members only and we have an educated professional moderator, David, that knows who to let through the gate :)
  • David ButlerDavid Butler Posts: 3,889
    @drdh, expensive electricity and reasonable gas rates in the Bay area argue against all-electric, but if that's your goal, then heat pumps would be the obvious choice for both space heat and DHW. If you have specific questions regarding mechanical systems, ask away.

    I don't have much to offer regarding residual smoke odors but it seems to me that carpet and drapes would be the only real concern, and in any case, those are usually tossed in a gut rehab. I imagine any odors that might have been absorbed by the building materials (floors, cabinets, drywall or plaster) would be remedied via refinishing. But his is way outside my area of expertise. You might want to consult with a company that specializes in fire restorations.
  • @Terry: Yes. There's a lot of overlap with public health, epidemiology, and atmospheric modeling, as well as toxicology and chemistry.

    I spend most of my work hours on the topics of "exposure" and "risk" to different populations/communities from emissions of ambient air pollutants in the SF Bay Area. I should say that the views and opinions I express on this forum (and elsewhere) don't necessarily reflect those of my employer, the Bay Area Air Quality Management District!

    I'll have a look at your "hot box" setup. Thanks for the link.
  • @"David Butler": Yes, I agree — at least for the time being. California is an interesting place to live in. The cap-and-trade experiment, and the ongoing restructuring of rates by the primary Bay Area distributor of both gas and electric (PG&E), have me wondering what is the best energy portfolio/system to bet on locally for the next 5–10 years.

    I'd love to ask questions about mechanical systems. Glad you mentioned it! ;-) Since we're basically rebooting the place, we're faced with a pretty basic choice in terms of how we approach heat and ventilation. I'm not religious about going combustion-free. Mainly, I'm wondering if I can plan a path that leaves being combustion-free a sensible option, again in a 5-10 year timeframe.

    One: we can opt for the more "traditional' route, with (1) forced-air heating, albeit with a high-efficiency, variable speed furnace for comfort and efficiency, plus (2) a separate DHW system. This would be relatively easy to communicate to contractors, and to the local Planning and Building.

    Two: we can go with hydronics, whether stapled between joists, run through ceiling panels, and/or home-run looped to zoned radiators. The latter seems like an interesting approach, especially for a retrofit. Currently, the second floor doesn't have any ducting running to it, and maybe it is a more "flexible' approach —sorry — to plan on running PEX (vs wide air ducts). Then we can do the ventilation separately.

    Naively, I like the second approach, because I don't see why the heating system and the ventilation system should be the same. It doesn't make much sense to me, unless you really can't separate them. (I would be very interested in different arguments on both sides of that fundamental question.)

    This is just how I see it now, so please correct me if you think the framing of the question(s) is wrong, or if we're overlooking some other basic strategies.

    Re: thirdhand smoke: this is the best empirical picture I've yet come across:

    "When smokers move out and non-smokers move in: residential thirdhand smoke pollution and exposure"

    ... though it leaves a lot room for a lot of follow-up questions. And of course a single study is never complete nor perfect.

    My limited understanding is that anything gypsum-based, like drywall or plaster, is after some years of secondhand smoke exposure essentially an "infinite reservoir" of third-hand smoke, at least at the rate at which it partitions from the gypsum into (nonsmokers') room air. Same with many other materials. Nicotine is very soluble, so it will work its way everywhere it can.

    I'm interested in consulting with environmental remediators, and I'm glad to post notes here about what I learn, if you think that'd be of interest to folks on the forum.
  • David ButlerDavid Butler Posts: 3,889
    Regarding ventilation... there are plenty of folks who would argue that ERV/HRV ducting should be kept separate from forced air ducting, so I don't see that as playing into the radiant vs. forced air decision. The problem is getting the ventilation system to balance when it's tied to a much larger blower that operates on call, and has radically different duty cycles throughout the year. ERV/HRV instructions typically include a diagram showing how to minimize this affect by connecting far enough back from the air handler. But that's a compromise at best.

    Another type of ventilation system relies on the main blower to draw in outside air through a filtered and calibrated orifice (Central Fan Integrated Supply, or CFIS). But this approach has its own set of problems. Here is an article from Building Science Corp, and here is a previous thread that dives into CFIS as well as exhaust-only ventilation. And finally, here is a recent blog by Allison Bailes on non-recovery balanced ventilation, which may be more appropriate for your climate.

    I know this will be seen as blasphemous to many of our members, but I wouldn't worry too much about ventilation unless you think you can reduce your infiltration by a couple of orders of magnitude ;)

  • David ButlerDavid Butler Posts: 3,889
    Regarding your heating system, there are too many variables to make any sort of recommendation. For example, lack of ducts in the upstairs shouldn't be an issue if you're doing a gut rehab. But I get the impression that's not what you have in mind (otherwise, you wouldn't be concerned about smoke-impregnated drywall).

    Depending on how deep you go with your envelop upgrades, a forced air distribution system doesn't necessarily require ducts larger than 6".

    Presumably your site has access to natural gas. That would be the obvious heat source if you want to do hydronics with radiant distribution. If you want to protect for 'combustion free' at some future date, a hydronic system will be a challenge. Air-to-water heat pumps are relatively rare, at least in residential sizes (does anyone know if Daikin Altherma is still available?). The only one I'm aware of that has a decent efficiency rating is the Chiltrix, which is imported from China by an east-coast solar distributor. I used the Chiltrix for an off-grid project near Phoenix last year that involved 5k gallons of thermal storage. The problem you're going to run into is finding a dealer who will stand behind an air-to-water system. Water-to-water (ground source) is more common, but I can't imagine the high cost would be justified in your climate.

    One thing I've learned working with homeowners, builders and mechanical contractors throughout the country is the further you get from vanilla, the wider you need to open your wallet. By far, the important thing is to have folks on your team who know what they're doing and will stand behind their work.

  • Yes, agreed. Luckily, the smoker didn't smoke in the upstairs bedrooms, so although there's probably some residual contamination, it's not immediately noticeable. I'm thinking the upstairs may be more conveniently served (for the next 5 years, till we get around to remodeling it) by mini-splits in the two bedrooms, and a modern fan + heat unit in the bathroom between.

    Re: heat pumps: There's a Heat Pump Water Heater workshop at my local library next month — I'll report back on what folks say about availability & value/cost of HPWHs here in the Bay Area now. NRT still has Daikin Altherma, at least on their website. The other brand I've seen folks recommending is Stiebel-Eltron, but as a European brand, I'm doubtful that it's easily serviced in California. Your comment about finding a dealer who'll stand behind the installation is well noted! Natural gas is definitely the most straightforward option here. But I do still want to get an idea of what could be accomplished "fossil-free".

    Re: ventilation, that blog post by Allison is actually what led me to your profile and this forum ... yes, I'm not terribly concerned about much now besides (1) giving the house slight positive pressure so that the airflow across boundaries (through leaks in walls, floors, ceiling, etc.) is in the right direction; and (2) plugging any giant holes in the envelope.

    For better or worse, and mainly as a matter of professional habit, I probably worry more about IAQ and less about energy efficiency (relative to one another) than most folks. That's just how I think about the world, most of the time.

    Thanks again for all the feedback! Still reading through old posts ...
  • Mr Holstius,, The last I knew Rob had left NRT and I think they have closed. Should call them before counting on something they offer.
  • Thanks for pointing that out, Edward! I didn't know.
  • David ButlerDavid Butler Posts: 3,889
    edited April 21
    Conversion from a gas furnace to a future air-to-water heat pump would be simple. Just add a hydronic fan coil to the furnace (along with appropriate pump and controls). If such a conversion is likely, you might consider starting with a gas fired boiler and hydronic air handler instead of a furnace. You could set up the boiler to supply DHW (sidearm or indirect tank). It could also be used to supply radiant zones for the upstairs bedrooms, although at least with mini-splits, you have the option of A/C during those occasional bouts of hot weather.

    Yes, NRT closed 3-1/2 years ago. Here's what I know about Altherma: About 2 years ago, a Daikin regional sales manager told me they were likely to discontinue in North America due to lack of sales. They had introduced version 2 in Europe but not North America, and a decision was pending regarding v3, which was not yet shipping. At the time, they still had some inventory on certain v1 sizes and configurations but not all, and SKU's that were out of stock were not being replenished. I haven't had any reason to follow up since then.

    It's worth noting that the v1 Altherma had poor efficiency (the model I looked at had 8 EER, IIRC) and was grossly overpriced, IMO. Dealer cost on the 2.5 ton split system (i.e., separate hydroblock) was around $8k (!) IIRC. As a point of reference, the 13 EER Chiltrix I used in the Phoenix off-grid project costs about $3k.

    RE: Stiebel Eltron: their US-distributed heat pump water heater is an indoor unit. You can't use that for space heat. They have a split system in Europe but I don't think it's sold in the US, at least it's not listed on the US website.

    @IAQ: as a practical matter, you won't be able to maintain positive pressure unless you do Herculean work on tightening your envelope. Changes in wind and stack will overwhelm any reasonable amount of supply air you would want to throw at it. The concept of maintaining 'slight positive pressure' doesn't make a lot of sense unless you have a really tight enclosure.

    If I were in your situation, I would find someone close to your site who can run blower door tests on your work, with an initial test to establish the baseline before doing any repairs.
  • Thanks again! Do you have any suggested pointers to schematics or writeups of such a conversion? (Case studies, diagrams, slide decks?)

    And thanks for the perspective on the positive-pressure goal vs tightening. I was wondering about that. I feel like a blower-door test would almost be comical at this point. But we'll get there ...

    Re: Stiebel-Eltron: I was looking at the Accelera® listed on stiebel-eltron-usa.com:
    In warm climates, an Accelera® is placed either in the garage, where it uses the heat from the outside air to make hot water, or inside the house, where it helps with the air conditioning load. In cooler climates, the unit is typically placed in the basement where it also acts as a dehumidifier.
    We do have a detached garage, as well as a "mechanical pit" in the form of a 10 x 10 ft corner of the subarea (crawlspace), dug out to about 5 ft below grade (the crawlspace is otherwise about 3 ft, measured between grade and the floor joists), which is where the furnace and water heater are currently situated. The crawlspace + pit and the garage are both far from sealed, and not "habitable", but definitely protected from rain, wind, et cetera. I'm not sure about code requirements locally but am asking our GC to look into that.

    Seems like that could be a workable option, unless I'm misunderstanding "indoor unit' ... ?
  • David ButlerDavid Butler Posts: 3,889
    Re: adding a hydronic coil to a furnace... No need for case studies, slide decks, etc. on something so simple and vanilla. But you do need a mechanical designer. This is not a DIY forum ;) If you start with a furnace, you need to make sure you leave enough clearance on the supply end for the coil and transitions. Your mechanical contractor can advise you on that.

    If you tried to use the Accelera for primary space heat, it would 'air condition' the basement or garage to the point that it will no longer work. For space heat, the evaporator MUST be outside. With a detached garage, it might work during the mildest weather, especially if the garage has good east and south solar exposed glazing. But you would still need a primary heating system.
  • Thanks again David for all the insights & feedback!

    No DIY tendencies here (apart from system design). I'm hiring a GC, and he's hiring the trade contractors. :-)

    I'm a bit confused about locating the Accelera indoors & using it for space heat. Could one not simply convey both supply (+ exhaust) air to (+ from) the unit using well-insulated ducting, keeping the unit itself in a utility closet?
  • David ButlerDavid Butler Posts: 3,889
    edited April 25

    No DIY tendencies here (apart from system design). I'm hiring a GC, and he's hiring the trade contractors. :-)

    By DIY, I was including the design part. Design is in many ways more challenging than installation, and is clearly undervalued in the residential HVAC market.

    From my perspective, every custom home or rehab project would benefit from a 3rd party mech design, but that's not how the market works. Once you sit down with your GC's mechanical sub and describe what you're trying to accomplish, you'll need to make a judgement as to whether you could benefit from bringing in a 3rd party designer. Often it's not because the contractor doesn't know his stuff, but he may try to push you into a design you're not interested in. Even if when the design part is straightforward, having a 3rd party specification enables you to solicit apples-to-apples bids from multiple mechanical subs. Allowing competeting contractors to drive the equipment specs makes it difficult if not impossible to compare proposals.

    I'm a bit confused about locating the Accelera indoors & using it for space heat. Could one not simply convey both supply (+ exhaust) air to (+ from) the unit using well-insulated ducting, keeping the unit itself in a utility closet?
    First, the installation instructions don't mention outside ducting option. You don't want to duct in outside unless the manufacturer explicitly supports this, and you certainly don't want to only duct the exhaust air, which you already acknowledged. In particular, the manual says if ambient air < 50F, it will energize booster heater (electric element) to ensure adequate capacity. You would have to verify that the sensor is positioned in the intake airstream (likely, but not guaranteed). Also, you would need to verify that ducting the intake air from outside wouldn't screw up the defrost algorithm.

    Second, given your electric rates, you certainly don't want to be using electric resistance for DHW or heat. In fact, I would advise disabling the boost mode if possible, or disconnecting the power supply to the element (must verify this with manufacturer). So if you wanted to use Accelera for space heat, you would a backup to heat the water and a way to coordinate the two. In your case, that would logically be natural gas. But if you need to install a natural gas water heater or boiler to supplement the Accelera, what have you accomplished? I don't know what your marginal energy rates are, but I'm pretty sure a heat pump water heater in your market will cost significantly more to operate than a natural gas water heater or boiler.

    Third and most importantly, Accelera's peak capacity (non-boost mode) is less than 6,000 BTU/hr. That's barely enough to handle DHW demand (only possible because of 80 gallon tank), let alone whole house space heat. As a point of comparison, a standard electric water heater has 15k BTU/hr capacity and a std gas water heater has a minimum of 25k BTU/hr (output).

    You seem to be going about your mechanical design backwards. Before considering which equipment or even the type of equipment for your home, you need to first get a handle on your design load, which is why I recommended having blower door testing done. Ideally you can hold off on mech design & install until you complete the bulk of your envelope repairs. Then have a proper load calc done based on the as-built condition and blower door test-out. If that's not possible, you'll need to establish firm specifications for your envelope repairs and get professional advice on a reasonable blower door target based on the current condition of the home and proposed work scope, then have a load calc done based on those specs. Once you know your design heat load is, then proceed with system design.