Building a new house in the Northeast: What heating system for cost and efficiency?
Hi – we will be building a new approx 2000 sqft modular home in Zone 4 Marine / Zone 5 (think its the 4 Marine).
The builder has recommended standard fiberglass wall insulation, says because it’s modular it will be tighter than stick-built, but can upgrade from new code with Upgrading to R 49 in attic (from R 38) and adding R7 rigid foam on outside. I understand that this is still short of the pretty good house standards, but it might be up to the code plus. We will also probably finish the basement with plenty of insulation (although how much is plenty).
House will have windows facing South-west, with first floor dark wood(ish) floors.
The builder recommends an “ultra-high efficiency” propane furnace and multi zone 3-ton AC. He does not recommend HRV system. We talked about getting house tighter and he said that the spray-foam insulation is quite expensive and would require whole-house HRV. I had thought this might be a more cost-effective way to keep house warm, so now I am confused.
Obviously, since we haven’t built anything, can’t perform load testing, etc. But this should be the tightest home we have ever lived in by far. We are scared of having dry furnace forced air heat, but being warned off the radiant floor heating by the builder (b/c expense) and this site. I originally wanted geothermal, but I don’t think we can afford it.
Our current home is leaky >60-year-old colonial with radiator. Newest home we ever lived in was tract-home built in 2000 in the south, but that one had (probably electric) forced air that was very dry. We had a very comfortable radiant floor in a very small cinder-block house in the the south, but I have learned from this site that the floor was so toasty probably because the insulation was so poor.
I think we could probably put in cold-climate air-source heat pump instead of the furnace and conventional ac, for about $3-4k more, but it will still be forced air. Does it have to be mini-split for cold climate? I expect that a gas fireplace in the great room can also provide much of the heating needs.
I expect that we probably will use the A/C system much less frequently than we will need heating. We are going to have ceiling fans to reduce the AC need as much as possible.
We can’t afford this as it is, but we don’t want to start on building something that’s not comfortable. So I guess our main question is for cost-effective, comfortable heating, as green as we can (not) afford. I just feel like we are fighting an uphill battle to try to be green here. Any advice is welcome.
Thank you
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Tell us your location so we can provide more accurate information. The builder's WAG on the HVAC makes me think you should not trust his advice. A 3 ton AC is likely vastly oversized for a well constructed house.
You say this is a modular house. Who is manufacturing the modules?
The location will be on Cape Cod in Massachusetts, which seems to have very expensive building costs. The modular manufacturer will probably be Westchester, as they seem quite a bit less expensive than Simplex. Custom designed.
Noah,
I'm not a fan of propane furnaces, but my objections have nothing to do with furnaces being "dry." A furnace won't make your home dry. Dry indoor air during the winter is usually a sign that the house is leaky. If air leaks are sealed, the indoor air shouldn't be dry, even if the home is heated with a furnace.
The main problems with a propane furnace are (a) propane is an expensive fuel, and (b) a green home shouldn't be heated with fossil fuels.
There isn't any reason why one or two minisplits should cost more than a propane furnace plus a split-system air conditioner. But if you are on a tight budget, and the furnace is cheaper, you may want to install the furnace. The key to reducing your heating energy bill is to have a tight, well insulated thermal envelope.
Thank you so much for your reply. It's only very recently through this site and others that I have come to see that electric heat could be greener heat, even if less efficient. Although with these different heat pumps it seems that we can have both, if we can afford it. I had really had my heart set on geothermal with radiant floors, but that was dashed by a very large price premium.
Any cost-effective building envelope improvements I should ask the builder to consider? I am a little overwhelmed by all the information and it sometimes feels like pulling teeth to get builders to consider greener options, especially if you want to keep your costs under $300/sqft in this area.
Thank you
Noah,
There are lots of article on GBA to help guide you.
For information on heating systems, see these four articles:
Heating a Tight, Well-Insulated House
All About Radiant Floors
Are Affordable Ground-Source Heat Pumps On the Horizon?
Just Two Minisplits Heat and Cool the Whole House
For information on green building basics, see these three articles:
Green Building for Beginners
Ten Ways to Improve a New Home
Ten Common Mistakes Made By New Home Builders
Noah,
FYI. Barnstable County is in Zone 5A. On Westchester Modular, it is a little concerning that they have very little construction detail on their website. I'm guessing that they use SIP panels to create the building envelope. Proper air sealing is particularly important with this approach. On the plus side, they do seem to offer a Energy Star option on some of their designs.
If it were my home, I would want to tour their facility and talk to several former clients.
Noah: If you are contemplating spending $600,000 on a new house, you might go the custom designed, custom built route, or try one of new England's energy efficient modular design build firms.
Steve Baczek is an architect in Falmouth whose designs have been featured in Fine Homebuilding Magazine and who is an occasional contributor here.
For design build modular:
Check out Brightbuilt Homes. Based in Maine, they design and build modular homes in New England. Go Logic is another option, as is Eco-Cor.
For $300 per square foot, you shouldn't have to settle for anything less than a highly efficient, beautifully designed home.
As for heating options, our experience with ductless minisplits in Maine has been totally positive.
I am trying to keep it to the $200 sqft range, which is probably why I'm having so much trouble with it (although it seems crazy to me). I am trying to stay at the $400k range, which is more difficult, but I still don't want to settle.
There are many builders doing really beautiful work in the $300 sqft range, but even then, there is a bit of hedging toward a higher amount. Thank you for the pointers, I will look them up.
I would think that if you are having good experience heating with minisplits in Maine there would be no problem whatsoever with them on the Cape.
Steve, while I think they can use SIPs, I don't think they do as a matter of course. I believe their energy star certification adds a bit of cost - I am trying to specify the performance rather than get the certification, but I guess that's what leads me down this incredibly deep rabbit hole.
There is so much information here, and its not always clear as to what's been done practically vs. theoretical. I wish I enjoyed this process more, but I am just getting confused and scared of making a wrong choice.
Thank you all for your help,
Noah,
I'm just a homeowner with an interest in residential construction and energy efficiency, so I understand the challenge you are feeling. I encourage you to follow up on Stephen's list of green-oriented designer/builders. You should be able to find a solution within your target budget.
(Personally, I wouldn't get too hung up on the 2,000 square number. Good design and space planning can make a compact footprint feel a lot bigger.)
You will save yourself immense heartache by avoiding companies that cannot demonstrate a comprehensive understanding of building science best practices.
Noah,
You wrote, "There is so much information here, and its not always clear as to what's been done practically vs. theoretical. I wish I enjoyed this process more, but I am just getting confused and scared of making a wrong choice."
All the more reason to take Stephen's advice to "try one of new England's energy efficient modular design build firms."
Here are articles on a few companies worth considering:
Kaplan Thompson's Modular Zero Collection
Vermod High Performance Manufactured Housing
Keiser Homes
Unity Homes
RPA-Ecocor
A 2000' code-minimum house with code-max air leakage on Cape Cod would typically have a space heating load under 25,000 BTU/hr (sometimes under 20,000 BTU/hr), at the 99% outside design temperature (about +12-14F) and a cooling load of about 1-1.5 tons at the 1% outside design temp (81-83F). In most cases you can heat and cool the whole thing with a 2 ton heat pump with 3kw of heat-strip backup and be covered down into sub zero temps, even for a box o' rocks dumb single stage non-modulating ducted heat pump, even if it just as stupidly had the ducts in an attic, above the insulation.
A better than code house that size can probably be heated and cooled with a 1.5 tonner.
A green-architect designed custom house can probably get you into the range where a 1-ton mini-ducted Fujitsu -12RLFCD has it covered.
The way propane works in most of MA you are usually effectively in a micro-monopoly, where the propane vendor owns the tank, and the exclusive right to filling it, with an abusive "removal fee" for making the tank go away. Low volume users tend to get abused (and badly!) by this arrangement. Even though MA has some of the highest electric rates in the US, at the statewide average prices for electricity and propane it's cheaper to heat with the heat pump. And since you live in MA you can choose cheaper grid energy suppliers than the utility, and rooftop solar pays off in a ridiculously short time frame (if you can get in before SREC-II is completely done.) But even with just the 30% federal income tax credit and NO state incentives beyond simple net metering (you still have some time on that) it's still cheaper than grid-retail from Eversource/National Grid, if you finance it at standard mortgage rates. Any way you slice it, bringing propane into the mix is a losing proposition- don't do it!
That "...dry furnace forced air heat.." is primarily a function of how air leaky your house is, and how well balanced the duct system is. Right-sized forced air heat with a Manual-D duct design that is commissioned with measured flow and measured duct leakage. With a decent design that's right-sized you'll still want the ventilation to be separate from the heating & cooling, and set the humidity levels during the heating season by adjusting the ventilation rate. With a modulating ducted heat pump the exit air temps are fairly low compared to 80% efficiency "scorched air" solutions, and the air flow rates are well below that of the typical 3-5x oversized fossil-burners you may have experienced in the past. Even a right sized 2-stage condensing fossil burner is very comfortable and quiet compared to what people have been living with in the past.
Dana,
Thank you so much for the helpful information. I think you just put the nail in the coffin of propane for me. I have learned so much from your comments here and on other threads.
Martin thank you for the pointers and all your great articles.
Thanks to all for your patience.
BTW: The proximity of water notwithstanding, Cape Cod is not considered a marine climate zone by DOE standards, since the prevailing winds are from the continent, not the ocean.
Also, central MA builder Carter Scott has been building true Net Zero Energy houses (PV solar included!) with 10-12" thick double studwalls full of half pound foam for under $200 per square foot. Most of his houses are on the cool edge of zone 5 rather than the warm edge (where you live). This price point was met even when PV solar was on the order of $5/watt (the national average is now about $3).
http://transformations-inc.com/awards/PDF/BE_MagFall13_OnLineFinal21.pdf
https://www.greenbuildingadvisor.com/blogs/dept/musings/just-two-minisplits-heat-and-cool-whole-house
https://energy.gov/sites/prod/files/2014/10/f18/BA_ZeroEnergyReady_Transformation_Custom_062414.pdf
http://www.thehomestory.com/net-zero-energy-homes-net-big-benefits/
Some would argue that their house designs trend toward an architecturally boring "shoebox with gable" side, but keeping the number of corners down helps with price/performance issues.
I'm not sure if Transformations has built anything on the Cape to date, but they're at least sort-of local.
Just to throw a wrench in this conversation... Martin recently recommended looking over at BuildingGreen for deeper conversations:
To my chagrin, the very first article references Drawdown (http://www.drawdown.org/solutions/materials/refrigerant-management):
It seems that the most important point to insulating (or over-insulating) may be eliminating the need for cooling. This, then would eliminate the need for mini-split heat pumps, and heating could be achieved without using high GWP refrigerants. One method of doing so is to use the Sanden HPWH which uses CO2 as a refrigerant. Another idea is to use the Sun Bandit to make your solar hot water a thermal battery and then use that in a hydronic system... Or we can wait patiently for the Nerdalize Cloud Computing heater (https://www.nerdalize.com/heating/) or Hotmine Bitcoin miner (http://en.hotmine.io/heater-miner#1) !?!?
The refrigerant release issue while a measurable slice of the pie, it is nowhere near "...the number-one action we can take to reverse anthropogenic global warming". Despite the high GWP all florinated gases combined only amounted to 3% of US greenhouse gas emissions in 2015:
https://www.epa.gov/ghgemissions/overview-greenhouse-gases
I suspect HFO1234_ _ variant refrigerants will be what replaces R410A in most heat pump & AC applications, not CO2 (though I'm a real fan of CO2 heat pumps, the pumps themselves are higher pressure and noisier.) Most of the HFO1234 variant refrigerants are single-digit multipliers against CO2 for GWP. A number of vendors are experiementing with R410A/HFO1234 blends as a replacement refrigerant for existing R410A equipment, but it would take an equipment re-design to go all HFO1234.
Insulation has only a small effect on cooling load once you're north of R20 in the attic, even though it's still cost effective to go for more. You'll never " ... be eliminating the need for cooling..." with insulation. With even modest insulation in the roof & walls the major driver of cooling load becomes solar gains through windows. But unless you live in a cave under LED lighting there are limitations of how far you can go there too.
Bitcoin mining has been seriously proposed as a solution to the "duck curve" of excess mid-day PV output, putting power that would have been curtailed to economic use. We'll see.
...sounds nice and cozy...
Sure- I can see it now, curled up on the couch with Klondike Bar in hand under the cool glow of an LED TV watching re-runs of the X-games snow sports edition from a comfortable dark cave in the Western Ghats, no AC necessary.
https://weatherspark.com/m/108945/4/Average-Weather-in-April-in-Munnar-India#Sections-Temperature
https://weatherspark.com/m/108945/7/Average-Weather-in-July-in-Munnar-India#Sections-Temperature
A very cozy cave indeed, were it not for the substantial LATENT cooling loads:
https://weatherspark.com/m/108945/5/Average-Weather-in-May-in-Munnar-India#Sections-Humidity
https://weatherspark.com/y/108945/Average-Weather-in-Munnar-India-Year-Round
Humans can adapt to life without mechanical cooling (as we have for eons) , but it has it's benefits, including quantifiable health benefits, and there's no way to really design out optimal health & comfort zone cooling loads just with building envelope design. That may be possible in some locations, but not as a general rule. Even locations as temperate temperature-wise as Munnar will still use mechanical cooling.
Save a Klondike bar for me - but how did we keep it frozen?
I love to go without AC as much as possible, and will have ceiling fans, but my work requires me to wear a suit, and I want to look fresh. I grew up in Miami, big cooling needs there - don't see how more insulation would ever solve that need.
If BuildingGreen has deeper conversations on these topics than occur here, it's probably not for me - my understanding is ]strictly limited to the kiddie pool for now.
Hi all!
Getting back to the suggested possibility of the $200 per square foot cost for a pretty good house; I am just not seeing it. Have been doing my research, and appreciate all the information on this site; but even the specific modular folks doing the passive or net zero house will put one well over the $200. (We are planning to build in mid coast Maine.)
There does appear to be a huge gap between the things that are out there and integrating them in application in an economically reasonable way.
And I am sure this has come up somewhere before, but electricity, if not generated by solar is generated in part by fossil fuels and there is a loss of power over distribution and transmission lines; so is propane really that bad? as much of the new electric generation is being fueled by propane?
This comes up for me because we are not willing to live with a ductless mini split due to the aesthetics and the one point source of the heat or air conditioning. We are considering the low velocity ducted heat pumps or radiant floor propane high efficiency furnace.
These are the threads of thinking around our plans; would appreciate any insight anyone cares to offer.
Thanks much
PS This is USER-6959515 or better known as Catherine T.
Catherine:
Nobody generates electricity with propane. Natural gas generates the largest share of power in New England. Propane is more expensive than oil for home heating.
If you are trying to stick to a budget, skip in floor heat.
I won't argue with an aesthetic concern, except to say that once installed, a minisplit blends into the background, just like every other appliance. The single point heat argument doesn't take into account that in a well constructed envelope, the temperature equalizes pretty well. It's thirty degrees, windy and snowing right now. I'm about twenty feet from our minisplit, right near a big window. There's no discernible difference in temperature from one end of our house to another.
I suggest not focusing on square foot pricing. Figure out how much you can spend and design accordingly. We are in Whitefield ME, also in the midcoast.
The grid mix in the ISO NE is only about half fossil-fired, most of it combined cycle natural gas at 40-50% thermal efficiency. The non-fossil stuff is mostly nuclear, with significant amount of hydro, followed by non-dispatchable renewables (wind & solar) and landfill gas, biomass. At any given moment you can get a snapshot of the current fuel mix on the ISO-NE grid here:
https://www.iso-ne.com/isoexpress/web/charts/guest-hub?p_p_id=fuelmixgraph_WAR_isoneportlet_INSTANCE_WQKSMAX9RozI&p_p_lifecycle=0&p_p_state=pop_up&p_p_mode=view&p_p_col_id=column-3&p_p_col_pos=2&p_p_col_count=5
The breakdown of the renewables hunk of the donut can be seen by clicking the tab.
The ISO-NE charts don't show what can't be seen by the grid operator, namely the contribution of behind the meter PV or heat & power cogeneration.
In Maine there is a substantial amount of wind power as well as hydro & biomass- more renewables than the ISO-NE grid as a whole.
Bottom line- a heat pump running even at a COP of 1.5 emits less carbon than a condensing propane furnace. If you can't stand wall-blobs, there are ducted mini-splits and 1.5-2 ton modulating heat pumps with bigger-deal air handlers that can meet your loads. They're more expensive up front than cheap propane furnace, but cost less to run, and have a much lower environmental impact.
According to EIA data:
"In 2016, almost two-thirds of Maine's net electricity generation came from renewable sources, with one-fourth from hydroelectric dams, one-fourth from biomass generators using mainly wood waste products, and more than one-eighth from wind. In addition, over three-tenths of net generation came from natural gas. The rest of Maine's net electricity generation came from petroleum, coal, and solar power.77"
https://www.eia.gov/state/analysis.php?sid=ME
Since 2016 there has been more solar (on both sides of the meter) and more wind commissioned. In that grid milieu heat pumps win the lower environmental impact contest over condensing propane by a large margin, and it's only getting greener-cleaner from here.
There is potentially a pent up low-carb disributed solar boom coming, once Maine is (finally!) rid of the LePage veto power.
https://bangordailynews.com/2017/07/10/politics/as-expected-lepage-vetoes-latest-maine-solar-energy-bill/
https://thinkprogress.org/solar-advocates-hope-lawmakers-will-override-veto-ed6499010825/
Being rid of the compromise destroyer LePage in combination with the power of the recent FERC Order 841 boosting the economics of distributed storage there's likely to be a significant uptick in the rate at which Maine's grid trends ever greener. The repeated breaking of consensus deals by stroke of veto pen has left all sorts of projects in limbo, awaiting policy-stability, but those days are probably coming to a close after the 2018 election, no matter who gets elected governor.
Thanks Dana and Stephen for the facts on the electric utility mix in Maine and other views about heating.
Yes, I believe getting over the wall blob is too much a hurdle for me; I am interested though in the most effective distribution system connected to the heat pumps. I get it on the cost of radiant, but had read that it is 30% more efficient than other distribution. And then there is the high velocity ducts(unicon); any views on these?
Steve, also wondered since you are in our neck of the woods, would you have suggestions for HVAC companies that are the best at thinking through and integrating all that is available for heating and cooling a pretty good house?
Appreciate the insights and anything you care to share!
Catherine T. again; still not certain how to get my name in the Answered By section.
Catherine. You need someone to calculate your heating load. Our architect used the Passive House Planning Package. You want a "Manual J" calculation . A good calculation takes wall and roof insulation, air tightness, window specs, etc. into account. While there are plenty of competent installers around, many just use a rule of thumb and end up oversizing the heating system. If not using an architect, look for a Resnet expert.
If you want to discuss in more detail, email me. Stephen at tidewater dot com.
Catherine,
Here is a link to an article that has helped most, but not all, readers with your problem: How the GBA Site Displays Readers’ Names.
For the minority of readers who report that the steps suggested in that article don't work, I unfortunately don't have any hints or solutions.
Until you've started to really nail down the actual heating & cooling loads it's premature to start prescribing potential solutions, but it's good to understand the options.
High velocity ducts have a higher blower power than better class low-velocity ducts. A lot depends on the motor efficiency and matching the motor to the load, but apples-to-apples there's only an efficiency down side to increasing the duct velocity.
Radiant isn't necessarily more efficient than right-sized ECM drive blowers if the pumps aren't carefully specified. The notion that has been claimed to be 30% more efficient on average in some field survey of (typically ridiculously oversized) systems doesn't really tell the whole story. At your likely very-low loads even assuming 30% better efficiency on the heat distribution mechanisms, a 30% better efficiency on something that's a nearly nothing fraction of a nearly-nothing total load doesn't matter very much. Getting a solution that is right-sized for the loads usually has a much larger impact on total efficiency. Modulating ducted mini-splits aren't bad, and the range of outputs available can be right-sized for a wide range of load.
If you're still enamored of radiant floors, a small reversible chiller might work for you. Rob Brown at Rockport Mechanical (http://rockportmechanical.com/ ) in Lewiston ME has design experience using hydronic air source heat pumps for radiant floors. (One of the first Daikin Altherma systems installed in this region was his design.) He would probably be able to design a heating/cooling system around a 2-ton modulating Chiltrix ( http://www.chiltrix.com/small-chiller-home.html ) to run as efficiently as a mini-split, assuming the load calculations are in the right range. (He'd be able to help you with those calculations too.)
NoahClem,
Having living on the Cape (Falmouth) for years, I'd say the need for AC is pretty minimal for most people. Never used for five years in N Falmouth in a typically insulated newer home, facing mostly west no less. Girlfriend used AC few days last year in E Falmouth, once the prior year.
Steve Baczek highly recommended, but may be too pricey or busy for you.
IMHO anyone pushing propane should be crossed off your list.
Agree with Dana, who knows more than us mere mortals! :-)
Robert: I don't know ANYTHING (you can even ask my wife! ;-) )- I just make it up as I go along...