jefferson17
New Member
Added: fyi on hot water needs. We have 4 showers. There is 1 bathtub upstairs (4th floor apt) but is used only for showers. Each upstairs apt has 1 shower. We have 2 showers in our unit (floors 1 and 2). It's just Amy and I in our unit. All shower heads (including ours) are Delta h20 kinetic - using 1.85 gpm.
>> I'd have to run the real numbers on the real construction to come up with a sort of real heat load number. The type of brick matters when it's 18-24" thick- something difficult assign a U-factor to, or even a range, but it's probably at least R5 (U0.20) from a thermal mass dynamic modeling point of view, and could be much higher. I assume this is a town house, and the other side of the common wall with the "twin" is a heated space (U-factor = 0.)
It's a victorian twin, not townhouse. So one wall is shared with the adjoining structure (except rear addition, which is open on 3 sides). The upper 3 floors are brick and about 8" thick. But that brick is pretty leaky, for sure. The lowest living floor has MUCH more thick masonry - about 18", sometimes closer to 24" We've had to drill through it so we really do know.
>> Any single pane windows with leaky or absent storm windows can cost-effectively be upgraded with tight-fitting low-E storm windows. Even though they are more expensive than clear glass windows, the payback is 5 years, not 10 due to the higher performance. The as-is clear glass storms+ single panes have a U-factor in the U0.5-U0.6 range. Tight low-E storms over those antiques would deliver U0.31-U0.34. Harvey makes the tightest storm windows in the biz, and have a low-E glazing option. The Larson low-E storms sold through the box store chains don't suck if you spring for at least the "Silver" version (the low end "Bronze" series leak a lot more air.)
Unfortunately, it's just not a good option for us. Replacement windows get quite expensive for our larger sizes. I've shopped around. Our house is also historical so more PITA. The payback would be at least 10 years - probably more like 15. Even more if we went with wood not vinyl. The money we spent on air sealing and insulation was well worth it though.
>> In the basement it's far better to put the foam on the exterior foundation walls that to cut'n'cobble between joists. This is for several reasons: Putting it on the foundation walls brings the joist edges and boiler completely inside the conditoned space, which means the wood stays warmer (= drier), and the standby losses of the boiler accrue to the conditioned space. Furthermore, it's damned near impossible (even with copioius amounts of spray foam) to really air seal at the basement-ceiling, but fairly straightforward at the foundation wall.
>> Unless you're using fire-rated Thermax you'll be required to put in a thermal barrier like half-inch gypsum over any wall -foam. An inch of foil faced iso and a 2x4 studwall with unfaced R13s might be cheaper, and would deliver ~R16 whole-wall (U0.06) after factoring in the thermal bridging of the studs. Keep the bottom edge of any polyiso off the slab, as well as the bottom plate of the studwall by putting it on an inch of EPS as a thermal & capillary break. (Polyiso can wick ground moisture, as does wood. EPS won't.)
Outside isn't an option but I appreciate the info. Hmmmm ... ok so maybe not worth doing right now. I thought I could just use double-foil 2" foam boards (I've got leftover of this stuff), but I guess it's not an option without installing a bunch of drywall too (PITA right now). We can get around to that when we get more drywall done in our rear addition next year.
>> 200 gallons on 3.5-4 weeks of "...really cold month..." isn't enough to go by, unless you have the EXACT fill up dates and a complete fill-up volume, so we can look up the heating degree-days for your zip code. But let's play the game anyway. The binned hourly mean temp for January in Bristol is ~32F according to weatherspark.com data, so lets assume a really cold month averages about 30F. That means that your heating degree day averaged (base 65F) 65F-30F= 35 HDD/day. You're burning something like 200gallons/25 days or 4 gallons per day.
I assure you that we burned about 6.5 gallons per day (averaged) for the 3 coldest months last year. We filled up some 200 gallons for 3 months straight and the interval was always 3.5-4 weeks. We certainly used about 1000 gallons last year, perhaps a bit more. That boiler is just a monster.
Of course - all of that is BEFORE we sealed the attic penetrations and filled it with as much blown fiberglass as would fit and before spray foam in rear addition (heat pump area), etc.
>> Are you still thinking 75K is "low" heat load number?
Ok ok - I'm believing you! LOL. So maybe 75K is high ... but after reading everything from you, it seems like 60-65K is at least pretty close and not "overly high". I'm going to look into getting a professional heat loss calculation done. That would be a worthy use of $100 I think.
>> If you can, add up the total fuel use in the past year. If it's under 800 gallons, any 50K boiler (condensing or otherwise) will cover your actual loads, assuming you didn't spend January in Belize with the thermostat turned down to 45F.
We definitely have used 1000-1200 gallons per year. But ... we also didn't add air sealing and insulation in the attic until march 2013 and spray foam in rear addition until may 2013.
Gosh I WISH we spent Jan in Belize . We have 2 apts upstairs, so even if we WERE away we'd still need to keep the thermostats set to 68-70. They are fully programmable, and I've got them set for wake, away, back and night - with separate settings for sat and sun. We need to keep us (and the tenants) comfortable. All thermostats are in our areas on the 1st and 2nd floors. The tenants can't change anything (but they can open windows if they get too warm in the winter).
Do you have any opinions on any specific high eff mod/cons? Here's one Buderus example, for discussions sake: http://www.pexsupply.com/Buderus-GB...odulating-Condensing-Gas-Boiler-Nat-Gas-or-LP.
I'm just thinking ... if 90% mod/con is $3300 and a Burnham ESC4 (78K) is $2264 that HOW MUCH GAS in $ would 90% "high efficiency" really save us vs an 84% ESC or similar? My wild guess is maybe $100 per year? So that's 10 years for an ROI. If the mod/con needs ANY professional yearly touch - that would be wiped out and why even consider it? Any thoughts?
Thanks!
Jeff
>> I'd have to run the real numbers on the real construction to come up with a sort of real heat load number. The type of brick matters when it's 18-24" thick- something difficult assign a U-factor to, or even a range, but it's probably at least R5 (U0.20) from a thermal mass dynamic modeling point of view, and could be much higher. I assume this is a town house, and the other side of the common wall with the "twin" is a heated space (U-factor = 0.)
It's a victorian twin, not townhouse. So one wall is shared with the adjoining structure (except rear addition, which is open on 3 sides). The upper 3 floors are brick and about 8" thick. But that brick is pretty leaky, for sure. The lowest living floor has MUCH more thick masonry - about 18", sometimes closer to 24" We've had to drill through it so we really do know.
>> Any single pane windows with leaky or absent storm windows can cost-effectively be upgraded with tight-fitting low-E storm windows. Even though they are more expensive than clear glass windows, the payback is 5 years, not 10 due to the higher performance. The as-is clear glass storms+ single panes have a U-factor in the U0.5-U0.6 range. Tight low-E storms over those antiques would deliver U0.31-U0.34. Harvey makes the tightest storm windows in the biz, and have a low-E glazing option. The Larson low-E storms sold through the box store chains don't suck if you spring for at least the "Silver" version (the low end "Bronze" series leak a lot more air.)
Unfortunately, it's just not a good option for us. Replacement windows get quite expensive for our larger sizes. I've shopped around. Our house is also historical so more PITA. The payback would be at least 10 years - probably more like 15. Even more if we went with wood not vinyl. The money we spent on air sealing and insulation was well worth it though.
>> In the basement it's far better to put the foam on the exterior foundation walls that to cut'n'cobble between joists. This is for several reasons: Putting it on the foundation walls brings the joist edges and boiler completely inside the conditoned space, which means the wood stays warmer (= drier), and the standby losses of the boiler accrue to the conditioned space. Furthermore, it's damned near impossible (even with copioius amounts of spray foam) to really air seal at the basement-ceiling, but fairly straightforward at the foundation wall.
>> Unless you're using fire-rated Thermax you'll be required to put in a thermal barrier like half-inch gypsum over any wall -foam. An inch of foil faced iso and a 2x4 studwall with unfaced R13s might be cheaper, and would deliver ~R16 whole-wall (U0.06) after factoring in the thermal bridging of the studs. Keep the bottom edge of any polyiso off the slab, as well as the bottom plate of the studwall by putting it on an inch of EPS as a thermal & capillary break. (Polyiso can wick ground moisture, as does wood. EPS won't.)
Outside isn't an option but I appreciate the info. Hmmmm ... ok so maybe not worth doing right now. I thought I could just use double-foil 2" foam boards (I've got leftover of this stuff), but I guess it's not an option without installing a bunch of drywall too (PITA right now). We can get around to that when we get more drywall done in our rear addition next year.
>> 200 gallons on 3.5-4 weeks of "...really cold month..." isn't enough to go by, unless you have the EXACT fill up dates and a complete fill-up volume, so we can look up the heating degree-days for your zip code. But let's play the game anyway. The binned hourly mean temp for January in Bristol is ~32F according to weatherspark.com data, so lets assume a really cold month averages about 30F. That means that your heating degree day averaged (base 65F) 65F-30F= 35 HDD/day. You're burning something like 200gallons/25 days or 4 gallons per day.
I assure you that we burned about 6.5 gallons per day (averaged) for the 3 coldest months last year. We filled up some 200 gallons for 3 months straight and the interval was always 3.5-4 weeks. We certainly used about 1000 gallons last year, perhaps a bit more. That boiler is just a monster.
Of course - all of that is BEFORE we sealed the attic penetrations and filled it with as much blown fiberglass as would fit and before spray foam in rear addition (heat pump area), etc.
>> Are you still thinking 75K is "low" heat load number?
Ok ok - I'm believing you! LOL. So maybe 75K is high ... but after reading everything from you, it seems like 60-65K is at least pretty close and not "overly high". I'm going to look into getting a professional heat loss calculation done. That would be a worthy use of $100 I think.
>> If you can, add up the total fuel use in the past year. If it's under 800 gallons, any 50K boiler (condensing or otherwise) will cover your actual loads, assuming you didn't spend January in Belize with the thermostat turned down to 45F.
We definitely have used 1000-1200 gallons per year. But ... we also didn't add air sealing and insulation in the attic until march 2013 and spray foam in rear addition until may 2013.
Gosh I WISH we spent Jan in Belize . We have 2 apts upstairs, so even if we WERE away we'd still need to keep the thermostats set to 68-70. They are fully programmable, and I've got them set for wake, away, back and night - with separate settings for sat and sun. We need to keep us (and the tenants) comfortable. All thermostats are in our areas on the 1st and 2nd floors. The tenants can't change anything (but they can open windows if they get too warm in the winter).
Do you have any opinions on any specific high eff mod/cons? Here's one Buderus example, for discussions sake: http://www.pexsupply.com/Buderus-GB...odulating-Condensing-Gas-Boiler-Nat-Gas-or-LP.
I'm just thinking ... if 90% mod/con is $3300 and a Burnham ESC4 (78K) is $2264 that HOW MUCH GAS in $ would 90% "high efficiency" really save us vs an 84% ESC or similar? My wild guess is maybe $100 per year? So that's 10 years for an ROI. If the mod/con needs ANY professional yearly touch - that would be wiped out and why even consider it? Any thoughts?
Thanks!
Jeff
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