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HVAC options?

R Yan | Posted in Mechanicals on

I need some help with HVAC planning for a duplex I am currently looking to build. It will be located in South West Manitoba aka Zone 7A from looking at the map.

I have a couple of options…
1) Stick built on site. This would give me the option of a slab foundation aka hydronic radiant heat.
2) RTM moved onto crawl space foundation. This would not allow for hydronic radiant unless I attached the lines to the underside of the RTM flooring (not inside a slab).

I know I could just go baseboard electric heat, but the monthly bills would definitely be higher. I do have access to NG so it would seem like a no brainer to go with NG to reduce monthly bills even further. I am kind of hoping to not run a furnace in each side as they would take up valuable space in the units. I am not completely against it however, if it is the best option.

I am looking for AC for the summers as well. I have been tossing up the idea of a split mini ductless, but they will most likely not suffice in the extreme winters we get (don’t want renters bitching about lack of heat).

What is the best option or combination of options while keeping costs relatively sane? Thanks!

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    R. Yan,
    Natural gas is a very affordable fuel right now. If you don't want to install ducts, and in-floor radiant distribution is awkward, why not just install a hydronic system with fin-tube baseboard distrubtion? Tried and true.

    Your best options for a heat source are either (a) a boiler, or (b) a tank-style water heater designed for combi-systems (for example, the Vertex from A.O Smith, the Phoenix from HTP, or the Polaris from American Water Heater, or the Combi2 TTW from Bradford White).

    The advantage of two furnaces (or ductless minisplits) is that it is easier to get the tenants to pay their own heating bills than if you install just one boiler and provide heat to both units.

  2. R Yan | | #2

    Yeah I definitely want something where each unit is responsible for their own utilities so two furnaces or two mini splits)

    In a new, tight construction build, how expense is baseboard heat? It would still be the cheapest/easiest to install initially, cheap to replace if need be, but the monthly costs would be a bit higher. I'm just wondering if its worth looking into something else or just let the renters pay the baseboard heat cost and be done with it? I would still have to duct in a HRV (mandatory code) and I add a mini split for AC in the main area.

    Any other thoughts or is that the way to go?

  3. Richard McGrath | | #3

    Baseboard heating does not have to suck anymore . There is very low temp baseboard available that has output exceeding the trash everyone has come to expect . Another thing about baseboard is how it is designed and run that has a huge impact . The world has gotten used to series loop baseboard where the temp at every successive piece on the loop receives cooler water then designed for . A simple manifold with homeruns to each room insures same temp water in all emitters , less feet per room , higher and easily achieved output . Heating edge baseboard is included in the link . It is an American owned company out of Randolph mass .

    http://www.emersonswan.com/ckfinder/userfiles/files/High%20Eff%20%20Guide.pdf

    This can easily be partnered with the HTP Phoenix or Phoenix light duty , the company that manufactures these also produces an OEM product /s for Giant , A Canadian water heater company .

    All in all , this would be very efficient . With the minisplit for cooling you'd have a winner .

  4. R Yan | | #4

    So if I was to go simple electric baseboard, the actual units themselves are cheap (very cheap if you get the basic ones), but then you have to run 240v to all of them. That means beefy wire and breakers for each. Cheap to replace a unit after the fact.

    If I went hydronic baseboard, the baseboard units are quite cheap. You only have to run pex (?) to them which is extremely cheap. But you would need a very high end hot water solution (Versa Hydro for like $7M each). You mention using a Phoenix, but a system would have to be built for heat exchanging with the closed system because that's not built into the Phoenix. Do you lose the room by room adjustability that the electric baseboard heat offers (controller in each room)? Or can you just adjust a valve for the water baseboard solution room by room?

    Sorry about all the questions. I'm VERY new to the whole baseboard heat thing.

  5. GBA Editor
    Martin Holladay | | #5

    R Yan,
    You wrote, "I'm VERY new to the whole baseboard heat thing." If that's true, then you definitely shouldn't be designing your heating system.

    It's OK if you aren't an expert at designing heating systems. You should consult a mechanical engineer or a qualified contractor -- one with good references. Don't make up these details as you go along, based on tips received on the Internet.

  6. Richard McGrath | | #6

    Phoenix would require an HX and 2 ECM circs ( 9-42 watts. You do not lose adjustability . You can put a tstat in each room and use actuators on the manifold or you can adjust the flow at the manifold and arrange piping differently from room to room which varies the output . In either case it is not as difficult as people believe . You could also use panel radiators with TRVs for room by room controlability and a wireless approach
    You should probably , as Martin mentioned find someone qualified to design it . I actually believe that is necessary in Canada to get approval .

  7. Stephen E | | #7

    In rental situations I find that using high quality PTHP's are an excellent choce and keep cost down. Think Hotel HVAC units but more quiet and higher effeciency. A plus side is the ability to do hydroponic and also gas heat with these unit. These units both heat/cool and have temperature control built in. On a tight construction they allow fresh air intake. No HRV required so further savings. $500-1000 on average installed. These units have electric backup for cold days.

    There is other good options, but for landlord/tennats PTHP's are the best. The savings on this system I would put towards getting a very air tight duplex. .

  8. Richard McGrath | | #8

    How much electric do they require SE ? Where as they may be good in a hotel setting where they are only used when there is a guest that is paying , maybe not so much for a residence where the tenant is paying . I'd rather my tenant have more of his money to try to insure he did not send my rent money to the utility .

  9. Stephen E | | #9

    The PTHP's I use run a 20 amp breaker. Have around 3 cop over 25 degrees. An example would be a duplex I renovated in zone 6. I went from a 280,000 btu boiler to around 24,000 btu's total for both units. The tenants around seeing around 90 percent reduction in heating and cooling. I spent the money on air sealing and minor insulation upgrade.

    Going to PTHP's to a mini split system could have save the tenants 1 or 2 percent more on utilities. Would have cost me 7,000 thousand of dollars more initially and more money if I needed to repair them later on. The clencher is that I got fresh air option and on demand heating. One of the main things on rentals is tenant behavior. Had on renter smoke weed leaving the window open when it was around -10 to -30 degrees. Their utilities where higher. Go figure. Is saving another 1 or 2 percent on utilities for the tenant worth it? Its up to you.

    Stephen
    Landlord

    Around the Ames, IA area

  10. Richard McGrath | | #10

    Of course they are seeing a 90% reduction in heating bills . You went from a surely short cycling therefore inefficient monster to a system 11.66xs smaller . No mystery there .

    Making the envelope better should always be done , regardless of what tech you intend to use . Could you explain what you mean by COP of 3 over 25 degrees ? I know what COP is , I just am interested in the language . Do you mean you are getting 24,000 Btuh using 2.3 Kwh ?

    How is the tenants hot water made now ?

  11. GBA Editor
    Martin Holladay | | #11

    Richard,
    There is no conversion factor for Btuh to kWh.

    Btuh is a unit of power, while kWh is a unit of energy.

    24,000 Btuh = 7,034 watts

    2.3 kWh = 7850 Btu

    A COP of 3 means that if you input 1 kWh of electricity, the output is 3 kWh of heat (10,239 Btu).

  12. Nate G | | #12

    Which PTHP do you use, Stephen?

  13. Stephen E | | #13

    Funny you should ask on the hot water. 30 amps per hot water heater. Uses more electric than the heating/cooling per unit. The only thing I could reasonably do is put a inline gas water heater before the 50 gallon electric water heaters. I'm in a too cold of zone to consider the heat pump water heaters. The problem with that solution is the inline gas heater set cost per unit at under 15 per month plus usage would negate some savings. I'm sure someone on this site has done the calculations so it possibly could be worth it down the road.

    The 24,000 btu's is max load of the duplex. Around 20 amps max usage per unit if below 25 degrees outside. So most of year using around 7 amps per unit.

  14. Stephen E | | #14

    Amana - There are others in the market as well. No complaints from the tenants yet. 3.5 kw backup electric heat in the unit at 11,500. I like using the TTW or mini pthp units at 26 inch width. Listed COP is 2.7 on that type of unit. Full size units have higher than 3 cop. There is a lot of options out their as well. Mini Splits, EPA wood burners are great options. Just something that has worked out well for me is the PTHP's.

    Down the road I look forward to replacing these with PTHP's that go below 25 degrees on the heat pump side. A simple 15 minute fix.

  15. R Yan | | #15

    I'm definitely going to consult with and have a pro install the whole system. That is a no brainer. I just checked and having natural gas to the home costs $14 per month for just the meter (per side). Maybe I'll skip it for now and just run purely electric. I'm thinking about a cheap electric HWT (easy to replace by me if need be) and then a Mitsubishi Mr Slim mini split in the main area for AC and some heat. I will most likely install additional electric baseboard heaters in the bedrooms to make sure there is sufficient heat in those rooms. This will probably be the easiest and cheapest for now. Probably not the absolute best as far as monthly bills, but I'm not paying those anyways. As long as I make the envelope tight, the heating costs shouldn't be too bad anyways. Thanks!

  16. Expert Member
    Dana Dorsett | | #16

    Since the mid-winter temperature averages in SW Manitoba are well below +25F/-4C, it's silly to be speaking of PTHP solutions there.

    It's also cold enough to run into the automatic turn-off feature of the Mitsubishi H2i series, which occurs somewhere around -28C. The Fujitsu RLS2H or RLS2H series don't have that issue and would be a better choice than a Mr. Slim in that climate.

  17. Richard McGrath | | #17

    Martin said , " 11.

    Richard,
    There is no conversion factor for Btuh to kWh.

    Btuh is a unit of power, while kWh is a unit of energy.

    24,000 Btuh = 7,034 watts

    2.3 kWh = 7850 Btu

    A COP of 3 means that if you input 1 kWh of electricity, the output is 3 kWh of heat (10,239 Btu).
    Answered by Martin Holladay, GBA Advisor

    Yes Martin , by using the first 2.3 Kw and making 7,850 BTU there was another 15,700 BTU delivered . COP of 3 = buy one get 2 free for all you KMart shoppers . Just to go over the math , 7,850 x 3 = 23,550 ( pretty close to 24,000) . Or we could say it like this , 2.3 x 3 = 6.9 (pretty close to 7.034) . You might also want to slow down a bit Martin , I believe BTU is energy and Kw is power , but I guess I could be wrong about that also . Martin , yes there is a conversion , I have seen you use it many times along with others . If there were no conversion we would never be able to argue electric against gas , propane , oil . In fact I looked just to verify that it can be converted and besides the several hard formulas in my office from every country in the world I found many internet conversion factors , tables , formulas . Here is just 1 ,
    http://www.rapidtables.com/convert/power/kW_to_BTU.htm .

    But keep posting Martin , I almost have enough to author my paper , All about Martin

  18. GBA Editor
    Martin Holladay | | #18

    Richard,
    You are still confusing your units.

    You wrote, "I believe BTU is energy and Kw is power." I agree. That's why I wrote, "Btuh is a unit of power, while kWh is a unit of energy."

    Btuh and BTU are different units; Btuh measures power, while BTU measures energy.
    KW and kWh are different units; KW measures power, while kWh measures energy.

    You suggested a hypothetical case where one could "use the first 2.3 Kw and make 7,850 BTU."
    But KW measures power, while BTU measures energy -- so you can't use 2.3 KW to "make" BTU.

  19. D Dorsett | | #19

    Seroiusly: Watts and BTU per hour are a rate of energy use, KWH and BTU are units of energy (that are not time dependent), but the units are metric vs. British.

    Mixing them up is exactly like referring to a distance of 100 miles as being 161 kilometers per hour. One is a fixed distance, the other is a speed. Distance and speed are not the same thing. BTU per hour or joules per second (= Watt) is not the same thing as as BTU or Joules or kwh.

  20. GBA Editor
    Martin Holladay | | #20

    Richard,
    I don't know how high my horse is. Usually I just walk.

    I started out at Shepard Corporation in St. Johnsbury, Vermont, at a minimum-wage job in 1975, working behind the counter. We sold boilers and furnaces to plumbers -- just a regular plumbing-supply outlet. Spent my days filling paper bags and small cardboard boxes with copper tees and Watts #2 valves.

    Eventually I started doing heat loss calculations for the plumbers buying heating systems. It was a very blue collar scene, pickup trucks and blue jeans, but no one confused BTU and BTUH. We had an old-school engineer at the branch in White River Junction who came up occasionally to do trainings, and he taught us that it was important to know our units.

    I wish I remembered everything he taught us about pump sizing. That was a long time ago.

    If a person wants to post a question or a comment on an automotive web site, it's usually a good idea not to confuse miles and miles per hour. They are different units.

  21. GBA Editor
    Martin Holladay | | #21

    Richard,
    I don't know who you were responding to when you asked the rhetorical questions, "Really? A kWh is not time-dependent?"

    The phrase "time-dependant" can have different meanings for different people. But a kWh is comparable to a gallon of gasoline or a cord of firewood. It's something that can be bought or sold. If I have a gallon of gasoline, it isn't necessary to specify how quickly or slowly I will consume it if I want to discuss it, buy it, or sell it. I can burn it slowly or quickly -- it doesn't matter. It's still a gallon of gasoline.

  22. Richard McGrath | | #22

    Seriously ? A kWh is not time dependent ? I really have to include h after BTU when the rest of the world knows that we heat and cool buildings in measurements of hours ?

    I mixed nothing up , when discussing heating and/or cooling homes or buildings we always mean an hour . We don't heat houses for portions of hours , or do we ? In the fields of heating and air conditioning the h is oft dropped because we all know we are talking about an hour . Maybe you folks from the building science side of the aisle should get off your high horse and start playing on the team where we all work toward a common goal . Or maybe you should not speak about heating and air conditioning buildings . Energy and power are intertwined
    let's see what some sources have to contribute .

    http://en.wikipedia.org/wiki/British_thermal_unit#As_a_unit_of_power .

    This is contained in the following , " When used as a unit of power for heating and cooling systems, BTU per hour (BTU/h) is the correct unit, though this is often abbreviated to just "BTU" )

    In the following text please see page 21 for a legend . On page 24 (heating) you will see that the manufacturer has 3 columns that state HC (heating content) kW (power) and HE (heat of extraction) . Please also note that the HC and HE are stated as MBtu/h and power is stated as kW .

    http://www.waterfurnace.com/literature/5series/SC2517WN.pdf
    '
    Dana , How long would it take you traveling 95 KPh to travel the approximately 287 miles from Bedford , Mass to Toms River , NJ ? Maybe we can discuss this over some food and beer at the Black Whale next time I'm in town .

  23. Richard McGrath | | #23

    Again , from the link above .

    " The BTU is often used to express the conversion-efficiency of heat into electrical energy in power plants. Figures are quoted in terms of the quantity of heat in BTU required to generate 1 kW·h of electrical energy. A typical coal-fired power plant works at 10,500 BTU/kW·h, an efficiency of 32–33%."

    http://en.wikipedia.org/wiki/Watt
    http://en.wikipedia.org/wiki/Kilowatt_hour

  24. GBA Editor
    Martin Holladay | | #24

    Richard,
    Yes, Wikipedia got it right. A BTU is a "quantity of heat."

    Ratings for boilers are expressed as BTU/H or BTUH -- they explain the rate at which the boiler uses fuel.

    Wikipedia is talking about a quantity (BTU). Boiler sizes are expressed in BTUH -- a "rate of consumption" unit.

  25. Richard McGrath | | #25

    And the same can be said for watts . A kilowatt is just a thousand watts after all . If you use 2.2 thousand watts in an hour you have 2.2 kWh .

    In the Water Furnace document I linked to do you suppose they mean that the unit uses 3.3kW in some amount of time other than an hour yet it has a heat content stated in MBtu/h ?

  26. GBA Editor
    Martin Holladay | | #26

    Richard,
    You wrote, "In the Water Furnace document I linked to, do you suppose they mean that the unit uses 3.3 kW in some amount of time other than an hour?"

    I'm afraid you are confused. Water Furnace is rating their equipment at 3.3 kW. It is a power rating, independent of time. One can use kW (in this case, 3.3 kW) to express either the maximum input power of the heat pump (electrical power) or, if one wanted, as the maximum heat output of the heat pump. This has nothing to do with time. If the unit is running flat out at its maximum setting, it uses 3.3 kW -- whether you happen to run it at that rate for 1 minute, 10 minutes, or 10 days. It's a rate of energy use -- independent of time.

    It's a little like a 100-watt lightbulb. The bulb uses 100 watts, no matter how long you use it.

    Similarly, you don't have to drive your car for a full hour to hit 100 mph. You can get to 100 mph in 5 minutes if you have a fast car.

  27. Richard McGrath | | #27

    Do you mean to have us believe that a 100 watt light bulb consumes 100 watts without being on for a full hour ? Please think about my question before answering .

  28. GBA Editor
    Martin Holladay | | #28

    Richard,
    Yes. You can confirm this with a Kill-A-Watt meter.

    We use "watts" to measure power draw. Even if it is running for just 30 seconds, it is drawing 100 watts.

    You are confusing power with energy.

    Kwh (or watt-hours) are used to measure energy.

  29. GBA Editor
    Martin Holladay | | #29

    Richard,
    This article explains the difference between power and energy, and discusses the units we use to measure power and energy: Understanding Energy Units.

  30. Expert Member
    Dana Dorsett | | #30

    While it's common to skip the ".../hour" or "...h" when specifying output levels of heating/cooling equipment or heating loads, there are many contexts in the written & spoken use where not being specific makes it ambiguous. You don't have to include the ".../hour" or "...h" if you don't care if it get's misconstrued, but for most of us clarity really counts in a web-forum format.

    Martin: "You can get to 100 mph in 5 minutes if you have a fast car."

    I dunno 'bout that ?!

    Zero to a hundred in 300 seconds / 5 minutes / 0.00000016 years seems like a pretty SLOW car- a car that wouldn't be able to sustain 100mph on flat ground in a 10mph headwind. My gutless Prius could probably hit that (but I'm not going to try.)

    Seconds, minutes, years, whatever- they're all units of TIME, right? ;-)

  31. GBA Editor
    Martin Holladay | | #31

    Dana,
    I said, "fast car." I didn't say, "a car that accelerates quickly."

    A car that accelerates quickly could certainly make it to 100 mph in less than 5 minutes.

    But if you want to hit 100 mph, you still need a fast car -- whether it accelerates slowly or quickly.

    Anyway, when I decide it's time to bring my old jalopy up to 100 mph, I like to roll down the windows and enjoy the scenery, and take my time getting there. With a little bit of a tailwind, I'm sure I'll hit 100 mph in 5 minutes. And at that point I'll be driving a fast car.

  32. Expert Member
    Dana Dorsett | | #32

    But pretty much all cars could hit 100 mph these days, they only vary in how long it takes to get there.

    The "... can get to 100 mph in 5 minutes..." implied to me that you were referring to acceleration, not top speed capabilities. Without the "... in 5 minutes..." I would have assumed it was referring to top speed capability.

    Speed & acceleration are not the same thing, but the term "fast" can be correctly applied to either.

  33. Rimonb5 | | #33

    In a new, tight construction build, however expense is moulding heat? it'd still be the cheapest/easiest to put in at first, low cost to exchange if would like be, however the monthly prices would be a touch higher. i am simply inquisitive if its price trying into one thing else or simply let the renters pay the moulding heat price and be finished it? i might still ought to duct in a very HRV (mandatory code) and that i add a mini split for AC within the main space.
    https://www.converterunit.net/

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