Heating and cooling size and installation help
I need help. I have read every article about heating and cooling on here over the last year.
Doing a deep energy retrofit on a 1956 ranch in Zone 6. I removed 36 k btu (500 btu ft) of cast iron baseboard and an oil boiler.
1000 sq. ft. 2×4 house has unfinished uninsulated basement, no floor insulation, no wall insulation and R-19 attic. No air barrier. Single-pane windows.
I’m doing open-cell spray foam rim joist, walls and top plate/ shallow section of soffit area with vent channel. Then R-60 + cellulose in attic. 2” polyiso exterior sealed seams, airtight drywall. 9 30”x50” casement windows, leakage .02 cfm sq ft, 0.27 U-factor.
Basement will get 1” XPS floor, 2” polyiso walls and R-30 batts between floor.
With Beopt I got about 12 k btu for heat and little less for cooling load. I think this is just for the main floor. Kitchen And living room are open. 3 br 2 bath. Will have ERV.
The two HVAC guys I have had are telling me 70 k btu furnace and 2.5-4 tons of cooling… I just don’t understand… one told me my heat load was 32 k btu by doing 3 seconds of math on his phone. Other guy would only do it if I let him out it in the attic.
I will be burying a 500 gallon LP.
I’m trying to go for comfort and cost-effectiveness. Refinishing the cast iron baseboards was my plan but it is not cheap. Then I would need a small mod con boiler with indirect for DHW. Or a combi with buffer tank as they won’t modulate low enough for heat load.
I thought about using a tankless water heater as the boiler and use a buffer tank and run cooler water through the baseboards.
The Rheem set up with tankless and hydro coil seems promising but nobody around me will install it.
I don’t feel a central minisplit will be enough to be comfortable in all rooms, they don’t make small enough units.
What would you do? Especially if you had to do all the work yourself.
If anyone knows a competent HVAC person who can do a real Manual J in Ulster county, NY, let me know.
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Replies
>"Doing a deep energy retrofit on a 1956 ranch in Zone 6."
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>"Basement will get 1” XPS floor, 2” polyiso walls and R-30 batts between floor."
At 2 polyiso doesn't even meet IRC code minimum for foundation walls in climate zone 6. (But 3" would.) A "...deep energy retrofit..." isn't a well defined term, but bringing it to at least code minimum would be a good start.
The 1" XPS on the floor is only warranteed for R4.5, but will in fact eventually drop to R4.2 when fully depleted of it's climate damaging HFC blowing agents. A 1" layer EPS of equal density is R4.2 now and will be R4.2 in 100 years. A Deep Energy Retrofit value might be the R10 recommended in Table 2 p10 of this document:
https://www.buildingscience.com/sites/default/files/migrate/pdf/BA-1005_High%20R-Value_Walls_Case_Study.pdf
But if you don't have sufficient head room, 1.5-2" of EPS (R6.3- R8.4) would be sufficient.
Installing R30 between the ceiling joists in the basement is not going to move the energy use needle very much, and possibly in the wrong direction if the boiler/water heater etc are in the basement, isolating their standby & distribution losses from supporting the heat load of the first floor. Invest that money in thicker foundation wall insulation and rooftop PV solar.
Get off the fossil fuel bandwagon. A heat pump water heater in the basement will dehumidify the basement. A mini-split or two to cover the main loads. (A couple of Mitsubishi F06 or FH09s would be about right, or a pair of cold climate LG LA090HYV1 for their ability to modulate to low levels at high efficiency). An electric boiler sized for 100% backup (4kw is enough) and/or for zone-heating with the re-used baseboards is inexpensive up front, and may improve comfort when temps drop into the teens or lower if some rooms get cold.
At the low temperatures you're looking at cast iron rads can be sanded lightly and painted with standard interior latex paints. With 72' of 9-7/8" cast iron baseboard your peak water temperatures would be ~115-125F to cover a 12K load. (I have two micro-zones using cast-iron baseboard running 125F water in my house- it's nice.)
[Edited to add]
Depending on the floor plan it could be reduced to a single somewhat larger mini-split and two zones on the baseboard using an electric boiler, so that the zone area covered by the mini-split doesn't compete with the hydronic system when heating the remote rooms less-covered by the mini-split.
Anything you might spend on propane infrastructure (like a buried tank), is likely to be better spent on PV to cover electrical used for heating. With a 12K heat load it doesn't take gobs of PV to hit Net Zero Energy on the heating bills if most or all of the heat is being leveraged by a cold climate heat pump. (It may or may not all fit on the roof of a 1000' house though.)
If propane is really mandatory, an HTP Phoenix Light Duty condensing water heater sized for the biggest tub you have to fill, with a simple exterior plate type heat exchanger to run the heating system works fine. In a higher-R house keep it simple- one zone, fixed temperature. With 130-140F water you have enough baseboard to cover Polar Vortex disturbance low temps without being ridiculously oversized or excessive cycling of the pumps. The minimum firing rate of the Light Duty is still twice your design heat load, but the thermal mass of the water in the tank keeps the burner from short cycling. Refinements such as outdoor reset mixers or mixing down the water temperatures to something super low doesn't really buy you anything worthwhile at such low loads.
I got a remote Manual J from this outfit and was reasonably satisfied: http://hvacsizing.com/
I am lucky enough to have blueprints for my 1935 house, making it easier to provide info for the Man J. The windows were replaced before I moved in, but Pella provided a detailed report, cutting down on the tedium.
They use Wrightsoft. There were a couple errors and oddball assumptions initially, though they were responsive in correcting them. I'm not expert enough to assess the correctness of some of the inputs, though comparing to the Ecobee-provided runtime of my boiler and A/C (both single stage) gave me confidence that it's close. It helped me with A/C replacement -- and not just overall sizing, but sensible heat ratio, too, since it's humid in the D.C. area. The boiler replacement will come later, though the Man J info is helping me think through how I want to handle it.
I'm with Dana on this one. Take the money you would spend on the propane tank, add in some extra insulation and go with a mini split. Depending on your electricity price, heating with a mini split will most likely be cheaper than propane.
With a simple single story layout and a basement, you can just mount and a ducted mini split in the basement ceiling to service the whole house. If you are careful with the ducting (larger ducts, minimum elbows, no flex duct) you can probably get away with a low static pressure ducted unit. This would be way cheaper than modcon+indirect+propane tank+separate A/C.
Instead of refinishing the baseboards, your time/money might be better spent in installing some heated floors in the entrance/kitchen/bath. If the floors are being replaced, electric mats are the simplest. If you are keeping the flooring, a staple up PEX install off your DHW tank is not too hard. A heat pump water heater should be able to heat around 200sqft to 250sfqt of floor.
>"With a simple single story layout and a basement, you can just mount and a ducted mini split in the basement ceiling to service the whole house."
If going the ducted route the 1.5 ton Fujitsu 18RLFCD is probably the right choice, but it's probably more expensive than a pair of FH09s. It has the capacity at low temp, but not the pan heater for the outdoor unit, so it needs to be monitored during extended cold weather use to make sure the defrost-water doesn't start building up ice to problematic levels.
There is also the Midea hyper heat units 18k or 24k that do ducted. They also OEM for a bunch of manufacturers (ie Lennox), so it might be easier to find an installer.
The turndown is not as low as the Fujitsu but has a pan heater as an accessory and a bit cheaper.
IMHO, Fossil fuel, and hydronics don't make sense in a low load home. (coming from someone who currently has both). I love my panel rads and aging Polaris tank(the HTP Dana mentioned is a much better, modern equivalent), but if I were to do it again I would've went ASHP all the way.
Agree with ASHP are the way to go with a bit of duct work or, electrical resistance where comfort or distribution is an issue. Since your basement is unfinished, it would straightforward to hang and duct a couple of compact low static ducted indoor units. 2 would probably do the trick, or 1 ducted for the bedrooms and bath, and 1 wall/floor head if your kitchen, living, dining area is open. Maybe one more 6kbtu wall/floor head in the basement. (go 1:1 splits everywhere if you can).
>" Maybe one more 6kbtu wall/floor head in the basement. (go 1:1 splits everywhere if you can)."
This house should DEFINITELY not be heated with a multi-split. The minimum modulation levels are way too high, and even the smallest 3-zone cold climate multi-splits would be 2x oversized, whereas for a multi-split to hit it's efficiency numbers it should be no more than 1.25x oversized. With separate mini-splits one or more can be turned completely off when loads are low. Only models that can run efficiently at low (<2000 BTU/hr) modulation levels should be considered if there is going to be more than one.
Unless the basement is going to be finished space with a high occupancy rate there isn't a good rationale for buying another FH06. The peak load is likely to be quite low (especially if the walls get 3" or more of polyiso in stead of 2"), and heating it with resistance heat only when occupied can be pretty cheap.
Thats for the fast reply's, i wanted to dig into the suggestions before responding.
Im glad to hear or maybe just assuming 12k heat load seems reasonable for my insulation/ air sealing plan?
Was planning to finish the basement at a later date, so the batts between joist are just to help for now and with noise. I also can get it for pennies on the dollar. For basmnet Was planning 2” polly and then build a 2x stud wall on top and insulate that with batts giving you above code min. Head room is an issue, fori can get more then 1” i will, Round here suppliers have hard time getting eps ...
Im back on track with my original plan. I was thinking a single mini split in the living room (12k) blowing towards the bedrooms. im hoping it will be enough to cool the whole house. I will attach a floor plan, I'm not sure how i could mount a second 1:1 with the layout in the bedroom hallway.
I like the idea of PV, how much would it take to service the house with 12k of mini split and ashp water heater? Around here its $10k per 3.3kw
The main reason for propane (buried 500g, $2500) is a standby generator for the family as well as to use a tankless water heater to heat the cast iron baseboards in 2 zones with lower temp water in the condensing zone. Should i get my dhw from this propane setup or from ashp water heater? Or i can use propane for now and go ashp when i get pv in a few years.
>"I like the idea of PV, how much would it take to service the house with 12k of mini split and ashp water heater?"
How much annual heating & cooling BTUs is BeOpt predicting?
Assuming right-sizing on the mini-splits you can expect about 10,000-11,000 BTU per kwh of electricity use, so divide BeOpts predictions by 10,000 BTU to convert that to annual kwh.
Then, what is the annual net uptake per watt of panel does PVwatts predict? (https://pvwatts.nrel.gov/index.php ) Take the time to adjust the parameters for orientation and roof pitch (if roof mounted), as well as any shading factors, etc., since that affects the amount of panel needed to cover it.
In my area a perfectly oriented & angled array with no shading factors would deliver about 1300 kwh/year (AC) per kw (DC) of panel after inverter losses, etc. Realistically in most rooftop installations it would be in the 1100-1200 kwh/year range. If my house were in Tucson Arizona it would deliver about 1750 kwh per kw of panel annually, with optimal tilt & orientation, maybe 1500 kwh/year in an average rooftop system.
The numbers relative to the heat pump water heater get a bit fuzzy, since water use can vary by more than 100% depending on the family, and 2/3 of it's heat is being supplied by the mini-split during the heart of the heating season, while it's lowering the cooling load during the heart of the cooling season. Using the EnerGuide label isn't going to tell the whole story. A typical plain old tank water heater's EnerGuide label is usually somewhere between 500-700 kwh/year. So taking a WAG at it cut that to something like 250-350 kwh/year to reflect the extra heating load and net cooling benefit aspects rather than a simple divide by three.
An electric boiler could run the baseboard for an installed cost of a lot less than the cost of a propane boiler, and is easier to right-size too. A heat pump water heater is still going to cost a lot less to run at about the same installed cost of a (hot water only) propane tankless. Even if the propane is serving as the "Hail Mary" backup for your other systems, electrifying everything in the house may still be the "right" thing to do, even if it means having to turn off the heating system while cooking dinner on the electric stove.
Dana,
That puts me in the right direction on determining solar, I will have this to reference back on when the time comes. I don't have solar in the budget for a couple years unfortunately.
Im on bord with the HPWH and have been doing some research on them.
For the electric heater for my baseboards are you referring to a tankless water heater? Im not sure how to size this. Im going to use about 62’ of the bast iron baseboard at .3gpf almost 19 gallons of water plus loop piping.
If my heat load is 12k btu and 1kw= about 3400btu id need about 4kw unless I'm missing something.
https://www.homedepot.com/p/Rheem-Performance-8-kW-Self-Modulating-1-55-GPM-Electric-Tankless-Water-Heater-RETEX-08/300800454
Im thinking one 12k 1:1 mini split like the samsung one you suggested mounted in the living room (above table in attached picture) facing the bedroom hall. Mounting even a 6k in the hallway will be problematic for several reasons.
I need to spend some time in bopt to make sure I'm comfortable with a 12k unit or slightly oversizing it.
>"For the electric heater for my baseboards are you referring to a tankless water heater? Im not sure how to size this as theres no btu, maybe figure out how much water is in 68’ of my baseboard would be a good start."
I'm talking about an electric boiler, not an electric tankless water heater. Electric tankless water heaters would all be too big, and can't handle heating system flows and duty cycles. Both electric boilers and water heaters are rated in watts, which is a metric unit of power. The conversion from watts to BTU/hour is 1 watt= 3.412 BTU/hr.
The volume in the baseboard is irrelevant. The design heat load of those rooms served by the hydronic system is what matters. If after running the room by room Manual J it all adds up to say 13,447 BTU/hr, in watts that would be 13,447 / 3.412= 3941 watts. At the 1.4x ASHRAE oversizing recommendation the biggest boiler size you'd be looking for is 1.4 x 3914= 5514 BTU/hr. Anything between 4.5-6kw would be fine, if that's where the numbers work out, but 6kw would already be more than 1.5x- don't go over that unless you absolutely have to. There are some pretty good 4.5kw units out there that would handle it, eg:
https://www.ecomfort.com/Electro-Industries-EMB-H-5/p18308.html
Oversizing by any more than 1.1x just means spend more money on fatter wire, bigger breakers, a bigger backup generator, all for zero additional comfort.
Dana,
You got to it before my edit, i did some research after posting on kw to btu. That is straight forward and thanks for the explanation.
I didn't even know about those small boilers. That would definitely have the lowest install cost as I have 95% of the hardware from the oil boiler I can re use as its not that old.
Im still hung up on having a back up generator that can run the well, water heater and boiler. I can do it with a 20kw unit but still need the $2500 propane tank. I am exploring options, power outages are very common where I am.
My power company central hudson has a $750 instant rebate for lowes AO smith heat pump water heater so I got it for $550! I almost want to buy a spare one.
Back to the insulation, I'm only able to find what they are calling felt or paper faced polyiso. One supplier called it fiberglass. There are all a few hours away as it it recycled material. My plan for the exterior walls is to use two staggered layers of 1” poly and seal the seams with hilti cp506 since I was given a couple cases.
For the basement I don't think I can use poly unless it is foil faced correct? I will try and find eps and tape the seams. Xps if all else fails.
>"For the basement I don't think I can use poly unless it is foil faced correct?"
NOT correct.
On the interior of basement walls paper or fiberglass faced polyiso works just fine. Just don't use polyiso on top of the slab under a subfloor.
The only caveat to insulating basement walls with it is to not rest the cut bottom edge of polyiso on a the slab where it can potentially wick ground moisture or minor flood water. If the basement has a history of flooding, stop the polyiso above the high tide mark and continue down with EPS.
In my own home the basement walls were insulated a dozen years ago with 3" fiberglass faced reclaimed roofing polyiso, stopping anywhere from 4" to 12" above the not-so-flat & level slab (which has sloped sections toward sumps with pumps, due to the high water table.) Almost every spring the local water table rises above slab level at some point, but the floor is kept dry by four sump pumps. More than once the power has failed long enough for almost the entire slab to get wet, but the polyiso & wallboard has stayed dry.
Hi, we are located in Rockland county and big on hydronics, manual Js, designs etc. feel free to reach out to me on Instagram.com/moespandh or my office phone threefourseven460HEAT. I'm certain we can be of assistance.
Dana,
Good insight, I may just search using the wrong words but there is so much content here it can be hard to find what I am looking for. I just installed footing drains and underground gutter drains. I waterproofed the wall and footing. My site is high with plenty of pitch away in all directions. I contemplated exterior insulation but chose not to for various reasons.
I want to have a continuous insulation and air barrier. Polly the floor and up the walls a few inches, as thick a slab foam as possible with subfloor and flooring. I was planning on running the poly onto the slab foam and sealing that joint.
I came across a note in my new heat pump water heater that says not to use a return loop. Im amusing it is ok to use a demand loop?
Moe i will reach out to you. Thanks
>"I came across a note in my new heat pump water heater that says not to use a return loop. Im amusing it is ok to use a demand loop?"
I'm a bit confused. To be clear, are you talking about ducting the heat pump water heater, or hot water recirculation systems? I suspect it's the latter. I''m pretty sure a demand type recirc where you manually call the hot water would be fine. There may be issues with short-cycling the compressor or something if using other control strategies for recirculation loops. (Just a WAG.)
Dana,
Yes I was referring to a demand hot water recirculate loop. Im adding the extra pipe so I can add a demand pump later. I centrally located the water heater so I may not need the Recirc.
Im using 3” paper faced iso on basement walls where I need my utility's to mount and a 2x4 wall in front. I don't have the time to finish basement now. But I don't want to have to remove all of my appliances to add insulation later.
Two Questions, is a 6 mil layer of polyethylene under the xps/eps a good idea? (i was given a bunch of 2” xps the wrest will be eps)
Xps and advantech have some permeability.
Finish floor will Probably be carpet to hide the unevenness in slab.
What is your thoughts on putting fiberglass in the 2x4 wall in-front of foam? Faced or Unfaced?
>"Two Questions, is a 6 mil layer of polyethylene under the xps/eps a good idea?"
Not necessary, doesn't buy you anything, and may increase the moisture content of the sill plate in some instances.
>"What is your thoughts on putting fiberglass in the 2x4 wall in-front of foam? Faced or Unfaced?"
In zone 6 as long as the foam is at least R7.5 (R10 is better) it's fine to install a fiberglass 2x4 wall in front of it, tight to the foam. Unfaced or kraft faced batts are fine, but not foil faced. Put an inch or two of EPS or XPS under the bottom plate of the 2x4 wall as a thermal and capillary break against the slab to keep it's moisture content bounded. If the basement has a history of flooding use only unfaced.
Leave a 0.5-1" channel between the foam and foundation at the slab to redistribute any bulk moisture that finds it's way through the foundation wall. The can be done by extending the bottom-plate foam under the wall foam, but not all the way to the foundation wall.
I will follow your advice for the basement insulation.
I spent some more time in beopt and also did a pencil and paper heat loss. Everything is around 12kbtu so I'm thinking the LG LA120HYV1 is the right fit. It may be a little big if my air-sealing works as well as I hope. But its has some impressive turndown rates that will cover heating and cooling very well. Its also a fair amount cheeper then Mitsubishi.
https://www.ecomfort.com/LG-LA120HYV1/p56907.html
Im moving towards a heat pump clothes dryer as I found a full size unit, whirlpool WHD560CHW.
I don't see much for reviews but the few hundred dollars more is offset by the ductwork and motorized broan damper for make up air. Plus the lifetime of savings from lower energy use and not bringing in unconditioned air.
Looking for some clarification.
As stated above my plan is two 1” layers of fiber faced polyiso on exterior framed walls. The Sil has no capillary break and sits directly on CMU blocks. I was planning on using open cell to seal the rim area to the top of the block wall filling the top blocks with foam out to the 3” fiber faced polyiso on the basement walls to maintain an air barrier. The basement floor will get the 2” xps/ eps with taped seams and advantek. There will be a heat pump water heater removing moisture.
This is what martin suggested to me a while back, but the other thread you responded to and further research has me questioning my plan.
Once the basement is finished the drywall would be the vapor retarder? But the utility room would need some type of vapor retarder over the open cell as the utility's Don't allow for sheetrock.
Looking for some insight into rafter venting, I'm concerned that the plastic vent baffles will get compressed by the open cell foam when we spray a thick layer on top plate/ attic parameter.
Is there a quality product? Or if i build them out of foam board what is the best material for spray foam adhesion? Will it stick to foil faced or xps?
>"if i build them out of foam board what is the best material for spray foam adhesion? Will it stick to foil faced or xps?"
Spray polyurethane foam is pretty much the same chemistry as Gorilla Glue (tm)- it sticks to pretty much everything, even when you might not want it to.
Dana Thanks,
I ended up going with the accuvent product, it stood up well to the open cell foam.
I custom fit the baffles between rafters as they are made for trusses. Instead of stapling the baffle to the interior of the top plate I nailed it on the exterior of the 2” foam creating a continuous insulation layer and air barrier. Any small gaps were filled when foam was sprayed. I plan on using a fine screen in soffit area to prevent any bugs from making that there home.
I still need to add the ridge vent, while reviewing code I was surprised to see ridge vent not required if you have enough soffit venting.
Adding Baseboard game plan question.
Now that we have lived in the house through the winter with just the 12k mini split, we want to add the cast baseboards for comfort. The mini split held its own but the bedrooms were noticeably cooler and the farthest one needs a space heater on 750btu to keep it warm enough. The .26u windows just aren't good enough. I had planned on using the electric boiler but doing the math and knowing how the wife uses a thermostat it will cost me a fortune. My highest Electric bill was $150 but with boiler i feel it will jump another $100 atleast.
I would like to use a condensing LP water heater. Im just working through how it would work if it even would, or I may need a buffer tank. my hope is the large capacity of water in the baseboards can act as a buffer tank. The units are cheep and I can get one with a couple gpm of 120degree water.
Any insight into this plan is appreciated.
Hi
if I recall we spoke on the phone a year ago.
on a few counts I feel you're incorrect.
1, glass is glass. better U value only helps so much. if you keep the shades rolled down you won't feel the radiant cool effect of the cold glass.
2, the electric boiler won't eat up as many KW as you think if you use the more efficient mini split to do the brunt work and bring the temp up to 65 or so and let the boiler subsidize the remaining 5 degrees.
3, an LP on demand water heater is NOT a boiler. A- its not rated to be a pressure vessel (H stamp). B- the unit is designed around large delta T and will likely short cycle and granted not give you the rated BTU if you run at a narrow dT. Done the math many a time.
Consider some fluid filled electric baseboards with a room by room thermostat so you can take the chill out of the rooms that are cold.
Moe from TurnUpTheComfort.com
Moe thanks for your input.
The windows are double pane low e argon .26 casements. They don't leak but the glass is cold. I imagine a triple pane window would be better? The biggest issue is design restraints, our bed and heads are by the two windows in room. Its not to bad, but on the coldest days of year we put a pillow against the window. The shades definitely help, I debated making some foam insulation plugs for winter.
I need to sit down and do some math on cost to heat whole house with LP vs mini split and supplemental electric hydronic baseboard.
I agree that using a water heater to supplement the mini split for 5 degrees would probably not work. But if its used for the whole load it seems more feasible. I may reach out for some consulting. I only plan on running 120-130 degree water through them as thats how I sized each room with existing units and to stay in condensing zone. A heat exchanger may be in order.
Its a shame that NY ended net metering, im not sure how vender is going to look but from all the solar companies its not good. If solar was still and option I would stick with all electric but its going to cost me more i believe.
I need to stick with the cast iron baseboards as I already roughed in for them.
Thank you
Touch base with me, we can help you with the math and we can bring the numbers back here for all to chime in on.
As for the windows, you will feel the same cold from triple pane as you will with double pane. You are feeling what is referred to as a radiant cooling effect. Window shades do wonders!