New Construction – Need Advice on Best HVAC System
I’m building a 2,600 SF one story Pretty Good House in north central Indiana (climate zone 5) with full 9′ basement of which around 2,100 SF will be finished. I’ve attached the floorplan. I’ve got R-10 sub-slab, R-5 rigid insulation on all the foundation walls studded out with 2×4 24OC with R-15 rockwool. On the main level, I’ve got 2×6 walls 24OC with R-23 rockwool, and Zip R9.6 sheathing. In the attic I’ve got R-60 cellulose all the way to the exterior walls with 20″ raised energy heals. I’ll be air sealing everything the best I can according to what I’ve read here and other places. Also, I’ll be going with all vinyl triple glaze windows (99% of which are on the East facing rear of the home) from MI Windows. They seem to be a pretty great deal at barely over $550 per 36″x60″ window. I got double pane quotes that were higher in cost!
Onto heating and cooling… I had a Manual J done by someone who specializes in just HVAC design. I’ll attach it here. I intend to have some sort of ERV. I’m trying to decide what the best HVAC system would be to install. I’m getting so many different answers from all the HVAC contractors I’m reaching out to. I originally wanted to do multi splits with a few heads (ducted and ductless) on each side of the house (upstairs and basement) going to 2 outdoor units. But I’ve recently read how those are inefficient. I’ve read minisplits, each to it’s own outdoor unit, are the most efficient, but probably the most costly?? I’ve read a lot of people here recommending one fully ducted air handler so you can filter the air better and tie your ERV right into it. My head is spinning with all the different opinions and options. BTW, I’m the builder, but this is my first home that’s not pretty much just code minimum. This will be my personal residence, so I really want to get it right, and not break the bank. Any recommendations or guidance would be most appreciated!
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What is your ultimate goal here? Are you trying to maximize overall system efficiency, minimize total construction costs, or find the sweet spot (which is probably also the hardest to do :-)? For maximum efficiency, minisplits with their own loops are probably going to win out, but they'll be expensive and harder to install, and more "stuff" to see on the exterior of the home. Multisplites with several heads and a single outdoor unit are a little cleaner to install, but probably not quite as efficient. You have to pick the tradeoff that best suites your requirements here.
If you go with a forced air system, you don't have quite as many options. You probably won't get the maximum efficiency going this route as you would with minisplits, but you get better air circulation, and a cleaner look in the house since you won't have "stuff" mounted in visible locations. This system will probably be the cheapest in terms of purchase price, but will likely cost more to install due to the need for ductwork, which takes more labor to install than a refrigerant line. Keep in mind all those minisplits also need electrical power run to them, so there is that too.
I don't see an issue with your insulating plan for the attic spaces and the above grade walls, but I would recommend changing your foundation wall plans. I would skip the studwall and use rigid foam for ALL of the required R value (which is now R15 in CZ5) here. Ideally, this would go on the exterior of the foundation wall, but installing indoors is often simpler. If you plan to finish the basement walls, I would use 2x3s on the flat to provide space for electricals, then drywall normally. I do not like to use fibrous insulation in basements.
Bill
I’d go with ducted - it’s the best way to match loads room by room, is the least intrusive and most flexible for backup and filtration. It might be slightly less efficient but your heat loss is so low, I wouldn’t chase it.
The goal is sort of the sweet spot, but I don't mind spending a little more if I can get a mini or multi split system to work. I'm kind of fascinated by that tech and would love to actually showcase it in my home. I don't mind the wall mounted units at all. They'd be a conversation piece. Currently, I was planning on 2 outdoor units, one on each side of the house and each covering several heads. I was thinking we could do a ducted in the basement with 3-4 runs to the master bed, bath, walk-in closet and maybe the laundry; then a wall mount for the basement covering everything but the basement bedroom suite, using air share fans to bring conditioned air into the craft room, office, and exercise room. That'd be it for the right side. Then, on the left side exterior unit, run a ducted unit to both main level bedrooms and jack and jill bath in between; one for the living room/kitchen/dining (upstairs office would be air share); and one more interior unit for the basement bedroom suite, probably another ducted unit supplying the bedroom, bath, closet. That'd be it - so 2 exterior units, one on each side, the right side supplying 2 heads (one ducted, one wall mount) and the left side supplying 3 heads (2 ducted, 1 wall mount).
If the interior units are correctly placed, then having 5 outdoor units would likely be way too much cost. One outdoor unit would likely not be a great idea. I was thinking the 2 units would be a happy medium for efficiency and cost. Also, if one went out, I'd still have another.
If you are thinking of hybrid approach, with both a ducted system AND some minisplits, then I would consider this (and note that what would make the most sense would be dictated by the layout of your home):
Install a full ducted system that could do everything on it's own -- don't try to use the ducted system for only a few rooms. This puts you in the "conventional HVAC system" house group, which does have some advantages, and it allows you to adjust the system down the road. It is very difficult to add ductwork after the walls go up.
Install a minisplit or two in areas that are occupied a lot as a percentage of total time the home is occupied. If you have an open-ish floorplan, this would put a minisplit in the great room / kitchen area, and possibly another in the master bedroom. What this does is allow you to use the minisplits as the primary heat (or cooling) sources in the areas where your family will spend the most time, with the ducted system helping out on really cold days, and taking care of the rest of the house. I would setup such a system (and I'm only going to talk about the heating season, but cooling is the same concept) so that the ducted system is a few degrees cooler than the minisplit areas, which means the minisplits do a lot of the "work", and the ducted system will help circulate that heated air when it runs to heat the rest of the home. This is almost like a zoned system, in a way. The master bedroom can also be conditioned seperately if you have another minisplit in there. You would then be able to adjust the ducted system and the minisplits to optimize the overall system, and take advantage of both. In some cases, you could probably let the minisplit do most of the "work" of heating, and just use the ducted system as an air circulator during periods of milder outdoor temperatures. During extreme cold, where the minisplit might struggle, the conventional furnace would be able to kick in and help with heating to maintain comfy temperatures.
Bill
When you say "furnace" do you mean a multi-position air handler, which would have it's own single zone hyper-heat exterior unit? Then you're saying have 2 additional wall mounted mini splits, one in the great room on the main floor, and another in the main rec space of the basement, each also having their own single zone hyper-heat exterior unit? Man, with 3 exterior units AND ductwork, wouldn't this be the most expensive option? And I don't think I could afford a 3rd mini split in the master BR suite... I never thought about doing both, though, with a hybrid approach. Interesting... I just hear that ductwork is expensive and the only way mini/multi split systems can be even somewhat competitive on price is because they don't need whole house ductwork.
I’d be surprised if ductwork is that much more and your CFM needs are very low with that heat loss.
Do you have quotes? Multisplits are also expensive! That’s why they’re usually put into retrofits, not new homes.
There is a lot of information out there which makes decisions very hard. When you step back a bit and look at only a couple of options make sense for a new build.
If you have a simple low load single story structure without much cooling, a single wallmount in the living space with supplemental resistance heaters in the bedrooms/bathrooms can work. This is very low cost, simple install and pretty efficient. This is also something that works great for an ADU.
Multi splits with a bunch of wall mounts is something for a retrofit (where it never quite works well and is expensive to install).
Outside of that you are looking at ducts.
With a low load single story structure over a full basement, anything outside of a ducted heat pump is adding cost and complexity for no benefit.
Looking at the floor plan, if you have the budget, you might want to put the main suite area on its own slim ducted unit as this will give you local control and reduce the duct run length a bit. You can also get a bit of limited local control without a separate unit by adding a damper to the main suite branch driven by a local thermostat.
The ducted heat pump can be any type as long as it is a proper hyper heat cold climate unit. Multi position air handlers tend to be the easiest for HVAC crew as they are about the same install as standard furnace. The slim ducted units also work just as well, they are cheaper and take up less space but they are not standard looking so your installer might quote you magical pricing. The way I've gotten around these is to have the installer only quote the equipment install (outdoor unit, indoor unit mounting, drains and refrigeration lines) and have somebody else install the ducting based on design.
With a high performance structure, you'll be looking at a fresh air system, ERVs tend to work the best in most climates. I find hybrid ducted setup the easiest to install. This is where the ERV feeds fresh air to the HVAC return and the stale air pickups are ducted to the bathrooms, kitchen area and basement. This saves you needing to install bathroom fans and associated wall caps so it should be about the same cost overall.
P.S. You man J shows 2ACH @50PA. Won't change your losses much but you should be able to half that without much effort. A decent ERV should be at least 70% efficient, so your ventilation loads should also be a bit less.
So if I did slim ducted units, wouldn't I still need to use several of them? 2 on the main level and 2 in the basement? I don't want any units or ductwork in my attic, so I'd be putting these all in my 9' tall basement which I do have 14" I-joists sitting on top of for a bit more room for ducting. Would it be best to put 2 ducted units to one outdoor unit and have one outdoor unit on each side of the house? This is pretty much what I was thinking originally, just eliminating the wall mounted mini splits that I was thinking could go in the main level living room and also the hug rec room in the basement. You think this would be better and cheaper than running the multi position air handler with full typical ductwork?
The only difference between a slim ducted unit and a multi position one is the blower size. This doesn't mean a single slim ducted unit can't heat a whole house, it just means it might need slightly larger ducting. Some of the units such as the Fujitsu ARU_RGLX mid static units can do up to 0.8" wg which is about the same as a multi position air handler.
Zoning makes sense when you have very different loads between areas of the house, things like sunrooms with a lot of glazing. Adding extra zones cost money and only save a small amount of ducting so it is something best limited. You also have to make sure the zone is sized for the unit, the smallest slim ducted unit is 9000BTU rated but most can do 120000BTU of heat, so about 1/2 your house load. Sticking a room or two onto a 9000BTU unit will cause cycling issues.
Your basement loads are low enough that it doesn't make much sense to have a dedicated unit for it. Lot of houses will need some basement dehumidification during the shoulder season and in summertime so planning for a built in one doesn't hurt.
There is no need to run any ducting into the attic. You can do all your duct runs through the joists if you use trusses. If needed, a couple of bulkheads in the basement are barely noticeable. The common setup here is to run the main trunk in a bulkhead in the basement ceiling along one of the outside walls. From there the supply runs can run up and along the joists for the main floor. Return should be a single large central return with a big filter grill somewhere in a hallway in the main floor.
Since the BOM cost between a two zone unit and two multi splits is about the same, the install cost delta is minimal, it is always best to have one to one units. These generally will have higher efficiency and better modulation range so going for a multi split only makes sense if you are tight on outdoor space. This also gives you a bit of redundancy which doesn't hurt.
If you go ducted, check out the CERV2. It's expensive ($8.5K?) but seems like the least complicated way to integrate whatever you choose for heating and cooling with optional whole house dehumidification and an ERV.
It's probably possible to accomplish what it does by tying together a 3rd party automation system with each piece of equipment as well, but more of a headache.
In terms of the number of heat pump units, keep in mind that for example two independent (not multi-head) 1 ton units running at half capacity is more efficient than a single 1 ton unit running at full capacity.
Ok, so here are my current options that I'm mulling over... Option 1 is zoning the house into 4 zones (see attached floorplan color coded with total room loads for each zone). For the green zone, a 1:1 ducted setup (PEAD-A12AA7 / SUZ-KA12NAHZ). For the red zone, a 1:1 wall mount (MSZ-FS09NA / MUZ-FS09NAH). For the blue zone, a 1:1 ducted (PEAD-A09AA7 / SUZ-KA09NAHZ). And for the purple zone in the basement, a 1:1 wall mount (MSZ-FS12NA / MUZ-FS12NA). Total cost of just the equipment is just over $9k, not including ductwork, line sets, etc. The other option would be to do the same 4 zones, but have the left 2 zones hookup to a single outdoor unit, and the right 2 zones another, so have two 2:1's. With that option, the equipment is $1,000 cheaper. Since I wouldn't have any tiny rooms on way too oversized heads, would I run into the typical problems associated with multi split inefficiency? The 3rd option would be to do a fully ducted setup with a multi position air handler (SVZ-KP36NA/SUZ-KA36NAHZ). The price of that is way lower at around $5,800, but then you have to run a full set up traditional ducting. You do have the benefits of better air filtration, potentially easier ERV incorporation if I choose to tie that into the air handler's ducting (which I realize isn't the best option), as well as only one set of equipment/filters to maintain/clean, etc. I know many of you have already given their opinions, but with these details, does anyone's opinion change? What would you do in a new construction situation? One of these option? Something different? Geothermal and get that 30% tax credit? ;)
I didn't see the separate Man J for the basement, the loads there for an R20/R5 basement seem on the high side, nothing jumped out at me as way off, I guess it could be the walkout with the larger windows, might be worth to ask your designer to check.
As for the equipment. I don't see why you would ever want a wall mount in a new build. You get point source heat, a box on the wall and something with almost no filtering that is very hard to clean.
Most of the units you picked are capable of higher max output at your design temp than their nameplate capacity. You are looking at installing roughly 54kBTU total capacity for a place with a about 3 tons of heat loss. No matter how you configure that, you'll get cycling. Put some of the heads on a multi split and it will be a lot of cycling.
Ducting is roughly priced by linear feet, there is a bit less ducting with slim units but not enough to change the ducting costs much. You also add in the cost of custom plenums for each extra air handler and you are not really saving all that much. Add units only if you actually need the zoning for areas with highly variable loads, your HVAC designer can recommend which areas need it. Looking at the plans, the glazing seems reasonable
Outside Mitsubishi, you can look at some of the other brands as well. All the other manufacturers offer a cold climate heat pump with a multi position air handler (Daikin, Fujitsu, Gree, Midea, LG, Samsung) which have similar performance and some are better value provided you can get local installation support.
For a new build, it is worth it to consider PV down the road. Small changes to the roof can make PV install much simpler and cleaner. If not set in stone, I would see what you can do to simplify the south and west facing roof sides. It doesn't mean the house should have a single pitch modern shed roof but a couple of small changes can make a big difference on PV install.
So I'm leaning toward the SVZ‐KP36NA & SUZ‐KA36NAHZ combo with normal ducting from everything I'm hearing. Sounds better, easier, cheaper, less maintenance... Do you think the heating capacity is going to be good enough though? It's only rated for 37,000 Btuh at 5 deg F and 29,600 at -13 deg F, but my total heating load according to the main level and basement Man J's total 39,000 Btuh. Can I just get the resistance heat added and let it run on the coldest days of the year? I remember someone posting how they actually undersized their heating load on purpose to only 80% of their total heat loss, then added resistance heating, and 98% of the time, it ran more efficiently? And I thought I remember it being someone smart, too. lol Or would it be better to find a unit with a higher Btuh rating?
You can talk to your designer and see where the model can be tightened up to make the system work (ie target air leakage, erv efficiency). Man J tends to oversize by default so there is always a bit of buffer.
The heat strip for all these units is also pretty cheap. You can install the small or medium one just in case. Might never run or for a couple of hours a year, small extra cost for a bit of piece of mind.
The P series are commercial units so they tend to be pretty expensive. I would try to stuck to the M series for cost.
You can also add a bit of resistance heat to the house (ie floor heat in the bathrooms) which will reduce the overall heat needed from the heat pump.
The NEEP site has a nice visualization tool for HVAC sizing. Click on the heat pump you are interested in and in the corner there is a "Advanced Data - Sizing for Heating" box. This will let you enter the design heat load of your place and give you a nice graph of what the unit will cover and how much cycling to expect.
P.S. Make sure to figure out your ducting plan as part of the design. Your floor plan is not simple and unless you are using floor trusses it will be hard to service some of the areas without larger basement bulkheads.
Or is this combo a better option: PVA-A36AA7 & PUZ-HA36NKA
I have been happy with my Rheem heat pump RP17 my house is about the same size and the back up heat strips are locked out when it is above 7° outside.
The bids attached to the first post shows 80% gas furnace?
Do you have city gas on your street? It is hard to beat for comfort and cost if you can get it.
At first glance the load numbers don’t seem over inflated.
Are you prepared to give up some basement head room to ductwork?
Be sure to keep all of your ductwork inside your conditioned space.
If you go with a ducted heat pump adding electric back up heat cost very little install and it will keep the house at the set point on the coldest days.
I like NEEP’s data base when looking at equipment.
https://neep.org/heating-electrification/ccashp-specification-product-list
Walta
Not sure why the Manual J says 80% gas furnace. I just didn't have the equipment selected at the time, and still don't, so maybe that's the default. Yes, I have gas line at the curb, but I was trying to avoid it. I'm building a Net Zero Ready Home. May try to add solar panels at some point. And from what I read, heat pumps are at least the same if not more efficient as gas forced air furnaces, and FAR more efficient than central AC. I have a 9' tall basement and don't mind soffits for ducting at all. Every house built in this area has them for forced air furnace/ac ducting. Thanks for the advice Walta!
" gas on your street? It is hard to beat for comfort and cost"
Comfort on modulating cold climate heat pumps is superior to any gas house I have been to. Unlike older heat pump technology, newer vapor injection compressors mean that the supplied air is hot even when it is very cold outside. There isn't that lukewarm air being blown at your feed from older heat pumps. Since they are also modulating they are supplying some amount of heat all the time so you don't get the typical burst of heat followed by long waits you get from a typical oversized gas furnace. Just nice even heat all the time.
Around me, a heat pump and natural gas is comparable operating cost.
"Unlike older heat pump technology, newer vapor injection compressors mean that the supplied air is hot even when it is very cold outside. There isn't that lukewarm air being blown at your feed from older heat pumps."
Got some numbers to go with this statement?
I fondly remember my gas furnace blowing 130°air. I am not saying it is impossible I don’t recall see anyone post a number over 116°.
What is your local gas and electric rates?
A heat pump may cost less in a few locations but not most and when the math says it does it is generally because they are cutting the pipe and subtracting the fix monthly gas fees.
Walta
I’ve never had anything but gas forced air/central AC. I look forward to having constant, even temps I’ve read you will have with the latest mini split tech, without the on/off 2-3 deg temp swings delivered by gas furnace/AC. If they’re even close on monthly cost, you can add PV to cover the heat pump, but obviously not the other. Look forward to that as well, hopefully.
Gas comes with other costs such as detrimental health effects. Hard to quantify economically, but the evidence is there.
Whenever I've check outlet temperature, with the fan on auto, it has always been above 100F, usually around 110F. I haven't check how high it can go, doubt it would hit 140F.
My gas cost including all taxes and fees $18/MMbtu. Electricity (again, all costs taxes and delivery) is $49/MMBtu, so if used by a heat pump, the heating cost is about 1/3 that so $16.
In my house, the only things that use gas is the boiler and BBQ. I can't see why I would keep the gas service thus the meter fee when the boiler eventually goes off gas.
It’s pretty common that gas is more expensive - i don’t believe a majority of US homes use gas for central heating. Places that have any real summer months (and thus AC and therefore electricity distribution asset utilization) usually can make the case pretty easily, since heat pump using gas generation uses gas more efficiently. Now, some utilities charge high fixed monthly fees for their gas infrastructure and bank on people paying $400/year to cook with gas, but if it’s a unit rate, gas gets expensive.
Your floor plan is not very open and has lots of rooms all over the place. So for the best distribution of fresh air and heated and cooled air I suggest a fully ducted heat pump air handler system with an integrated ERV or HRV and humidifier (if needed in your area). This "looks" like a traditional ducted furnace system so you will get less of a "it's new to me" cost premium. The ducts move the fresh air to and from the ERV most of the time, but oversize them so when you need recirculating heating and cooling the same ducts can be used without being noisy.
Making you floor plan more compact with less jogs and bump outs will increase the efficiency of the house significantly. You also have your bathrooms on opposite side of the house, moving them closer together will improve energy efficiency and effectiveness (less wait time for hot water to get to the faucet).
Floorplan is actually very open concept. Got the master suite on the right side, kids bedrooms on the left with jack and jill bath. Office at entrance. To die for pantry. Basement rec area is like 1,800 SF of open area. Are you talking open as in Little House on the Prairie style where everything is in one room? If that were the case, it'd be one mini split all the way! lol Anyway, I am now leaning toward the SVZ‐KP36NA & SUZ‐KA36NAHZ combo. It's a Mitsubishi hyper heat outdoor unit tied to a multi directional air handler that would be hooked up to whole house ductwork (what you normally find tied to a gas forced air furnace/AC setup). Will definitely be integrating an ERV or HRV into it as well.
So do any companies have a hyperheat (or similar tech) with an indoor multi directional air handler that uses a true variable speed ECM blower? From what I'm seeing, Mitsubishi's doesn't. It only has the x-13 type ECM that has 3 speeds? Is that a big deal? It doesn't seem like that would pair well with the variable speed outdoor unit. Wouldn't it cycle on and off all the time if it didn't have the ability to utilize the "barely but constantly heating/cooling" ability the outdoor unit provides? If I'm tying the ERV into the main ductwork and relying on the Mitsu's blower to circulate the fresh air, won't that cost a fortune and defeat the purpose? Or does just mean I would have to run separate supply ducting then to avoid that?
Would it be best if Mitsubishi had a variable speed blower? Probably. It’s not really worth it though - I have the SVZ/SUZ combo and it runs on the lowest fan setting nearly constantly. If it was fully variable, I’m not sure how much benefit there is - the outdoor units can’t turn down all that much and you’re chasing diminishing returns. It’s comfortable! Furnaces can’t touch the level of comfort.
Cool. Thanks Paul! If you have one, how did you handle ERV/HRV integration?
New question... do I need my basement and main floor to be on separate zones/ductwork? Would it be necessary to have 2 separate air handlers, one for the main level and one for the basement? I'd rather keep it simple and cheap, but if my thermostat is upstairs, I can't help but think my basement will be much either overcooled or overheated. Is this true? What's the best way to go here?
About the only time I've seen separate HVAC for a basement is when there is an ADU. Outside of that, basements share the air handler.
The simples is to have takeoffs for the basement with adjustable registers, this tends to be the most common setup. Most newer construction tends to have pretty even temperature, once set up, you generally don't have to adjust anything.
The next one is to have a dedicated supply trunk for the basement with a balancing damper. This lets you adjust the flow for all the supplies in one shot, typically the damper is marked summer/winter positions and you change it twice a year.
If you want better you can add a motorized damper to this trunk driven by a local thermostat. As long as this damper doesn't close all the way or the rest of the ducting in the house is sized to handle the additional flow when closed, it doesn't need any integration with the air handler.
The answer to your question depends on how you will use the basement and your expectations.
If the basement is all unfinished storage space it is very different than if the basement is an air B&B suite.
My basement is mostly shop space and exercise room. It is generally a little cooler in the basement and I am fine with that others might not be.
If you do a good job air sealing and insulating you will not have much in the way of hot and cold spots everything will be more or less the same temp.
Walta
Most of the basement will be finished. There's a bedroom suite down there, an office, a craft room for my wife, an exercise room, and a huge open space for games, movies, hanging out, etc, so we'll definitely spend a lot of time down there. The entire back wall is daylight with a pretty good amount of windows. The heat load down there is 16,152, while the heat load on the main floor is 22,711. My main concern isn't to have zones with different temps. I just don't want one area way too hot or way too cold like every house I've ever had in the past. I'd be totally fine with just even temps everywhere. That would actually be miraculous!
My insulation values are:
R-10 SUBSLAB
R-20 FOUNDATION WALL
R-60 ROOF
R-32.6 WALLS (Zip R9 outside, Rockwool inside, 2' OC )
R5.5 Windows (triple pane .18 U-factor)
Shooting for 1-2 ACH50 (giving myself a little leeway since I've done this before)
If I can be ok with just one air "hyper heat" variable speed air handler and just close my basement vent a little, and still have similar temps in basement and main level, that would be great!
My house is slightly smaller but similar insulation. I chose two slim ducted air handlers one for the main floor and one for the basement. I was able to get all my ducts for the air handlers and a separate erv duct system in my floor joists. My joists are open web and 19” tall. I attached the design. I have been pleased with the result but I have not moved in yet.
So based on your all's recommendations, I've decided to go the fully ducted multi directional air handler route. Mitsubishi's option needed to be commercial (42,000) to cover my heat load. Fujitsu's residential 48,000 btu hyperheat model (48LMAH1M) seemed to have a better indoor air handler and was cheaper, so I was thinking of going with that. However... it says on the submittal that it's NOT Energy Star rated. How could this be? From what I read online, this means I won't get the $2,000 tax credit. Is this unit not as efficient as others? I was going either Mitsu or Fujitsu's heat pump because I thought they were the industry leaders in efficiency. Are there fully ducted multi directional air handlers that ARE Energy Star rated that would qualify for the $2,000 tax credit, that would be better options?
Any reason why you aren't considering multiple smaller capacity units instead of one big one?
That was my original plan but several people in this thread recommended since it's new construction to do a fully ducted setup.
Ah ok. Maybe my level of understanding isn't quite there but I was under the impression you could hook up multiple smaller capacity units to one set of ducts.
I Think it is a risky play to select any heat pump that has not been tested and submitted to the NEEP heat pump list.
https://ashp.neep.org/#!/product_list/
Will you have electric strip heat as a backup installed?
You may not need it but the install cost is low and when some part is on order for a week as happened to my Rheem earlier this month is made it an inconvenience instead of an emergency.
Walta
The only ones that are Energy Star rated on the NEEP site are Carrier and Bryant, but neither are 100% efficient down to 5 deg, so not "hyper heat", or LG (Outdoor Unit Model #: LUU420HHV / Indoor Model #: LVN420HV), which does seem to have "hyper heat" ability. I thought Mitsu and Fujistu were the best and had the best technology, most reliability, etc.
Yes, I will add the strip heater added.
So I opted to go with the Fujitsu 48LMAH1M multi directional air handler with full ductwork. I like that I can incorporate one whole house filter, MERV 13 and even higher, right at the unit. Now, onto my ERV questions. What's the best option, Panasonic Intelli-Balance 200 or the Broan 250 CFM HE? They seem to both have the proper capacity. I'm planning on only doing a constant 70-80 CFM, with boost up to 200 or so. My quote from my HVAC installer to install separate return ducts to each of my 4 baths and separate supply to each of my 4 br's was $4,800, that's on top of the cost of the ERV. That's more than I want to spend. What are next best options? Since I have whole house ductwork, I know I can dump the fresh air into the cold air return. I've read that increases my electric bill by a lot since it relies on my Fujitsu's fan to recirculate it. Is this going to be significant? Open to thoughts and suggestions.
Either ERV should work.
I like hybrid ducted setup with stale air pickups in bathrooms/kitchen/basement and fresh air feed to the return. Works almost as well and much cheaper ducting plus it conditions the fresh air feed to the house.
Once you take out kitchen and basement airflow, a 200CFM unit won't be enough to clear 4 bathrooms though. I would only put two of the most used ones on the ERV and use a standard bath fan for the rest.
The blower energy penalty is mostly an issue with older PSC blowers. Most modulating heat pumps have much more efficient ECM blowers and run the blower 24/7 already, so there is no additional energy penalty. You don't even have to interlock the blower to the ERV, for the odd rare time the blower is off, the fresh air will simply be supplied to the house through the return vent.
Akos, what would you recommend for this house as far as constant CFM and boosted CFM. It's 2,600 SF main level, 2,100 finished in basement. 3.5 baths. I'm a little confused as to which formula is right with all the different ASHRAE standards that keep increasing it, then you have Joe saying it's way too much. I have 7 people in my family, but one's in college and only lives at home in the summer, another is about to go and do the same... Is 80CFM constant ok? Maybe aim for 12 CFM constant at the 3 full baths (I know you said 2, but one is literally on top of the other and the duct is right there, so I figured it makes sense just to run it's venting through the ERV, too. So 12CFM in each bath would be 36, leaving 22CFM for the basement and great room on the main level. Then boosted to double? Or do you recommend more on the boosted? Thanks for all your thoughts. You've been most helpful on this build!
I would go by your local code (I've attached from mine, 1L/s is about 2CFM)*.
I would size the boost to provide about 2x your ventilation requirements. This also gives you a bit more room to crank up the ventilation if there are more people at home.
A bathroom needs about 50CFM to clear it properly, about 2x that for a steam shower, so 12CFM(or 24CFM on boost) is not enough, at that point you still need to include an exhaust fan. The simplest is limit the number of baths on the ERV so you can get proper flow to them.
*Some of the ventilation there is exhaust, not all of it needs to be supplied fresh air.
So if I set the boost to 50 in all 3 baths, and 50 in main level great room and 50 in basement main open finished area, that would put me at 250 CFM, the max for the Broan ERV250TE. That would work ok, right? If so, what about in non-boost continuous mode? Just set it to around 35% of boosted to put me around 87.5CFM, split evenly between the 5 areas (~17.5CFM each)? When my older kids are at college, I could close the vent in the downstairs bath since it won't be being used, which would split the 87.5CFM between the remaining 4 areas (~22CFM each).
Forgive me. I'm an HVAC mechanic with some experience but I'm completely new to the nuances of passive homes and system designs. Trying to do some research to learn what I can. If I'm missing something I hope someone can fill me in...but...
Your manual J load calc is calling for just over 1.5 tons of capacity for the 1st floor and just under 1T for the basement, yet the Fujitsu 48LMAH1M is a 3.5-4 ton unit. This sounds like overkill for anything resembling a passive-type home.
Is this oversized or am I missing something here?
The heating load for the home is 3.2 tons…
Hi,
did you find a model which allowed you to get the $2,000 rebate?
No need to apologize at all! It's great to see you doing your research and seeking advice on HVAC system designs, especially for a new construction project.
Based on your manual J load calc, it does seem like the Fujitsu unit might be oversized for a passive-type home. It's essential to match the HVAC system's capacity to the specific requirements of the space to ensure optimal performance and energy efficiency.
For more insights and expert advice on HVAC system designs, you might want to check out http://dynamicheatandcool.ca/. They could have valuable information and solutions tailored to your needs.