HVAC New Construction Advice

pfm

Hello all,

Looking for advice from both professional installers and from HOs who live with these systems. We are having a new house built in southern NH for ~3000 sq ft for a family of 4 with 2 floors and a finished basement (not walk out). Builder has quoted work based on an Energy Star v2 (2012 standard), LP Forced Hot Air furnace at 95% AFUE, 16 Seer A/C and a tankless water heater which is similar to our prior house though we had a 40gal hot water tank; so, we understand the pros and cons of this system; the property has town supplied water, but will have septic/leach and may be sitting on a fair amount of ledge. We are having a full-house LP generator installed having lived through 4 back-back years of 5 days with no electricity and will be using LP for at least cooking, possibly laundry dryer and, thus, as a heating fuel source though it is quite expensive (and highly variable year-year) as is electricity. I will likely try to understand from the Builder the costs to either super-insulate the home or go for Energy Star v3.x.

Have been researching options of Hybrid, Hydro-air and Geothermal, but as there is no well drilling planned, ducts installed and as LP is still needed, I am thinking the first 2 are the only other 'reasonable' cost options though we are willing to invest up to 50% more up front for lower operating costs and year-round comfort over a 10-15 year timeframe. In our area, the HSPF is only ~5.5; so, compared to just propane, an air-source heat pump would be less expensive particularly some of the newer systems that are efficient at lower than 40 degree temps. I realize that with Hydro-air, I would get unlimited hot water, but wouldn't there be efficiency losses in the transfer from the heated coils to the blower for heat distribution through the ducts? I have looked at rooftop active solar and/or wind turbines to 'pay' for the additional electricity to run the HVAC system, but that does not seem to be advised in other forums due to lack of ROI.

What I am struggling to compare is the annual 4 season operating costs between the builder proposed solution versus a hybrid or hydro-air system all other factors being equal to make an informed decision on a cost and comfort basis. FWIW, the wife is fine with scorched air and the drafts...

Thanks much in advance.

Gordy

Insulation is the gift that keeps on giving.

Any chance that the future holds NG in it for fuel?

Steamhead

Builders generally propose whatever is cheapest. They don't have to live with the results. You do, so does your family.

I would not recommend any type of forced-air heat at all, including hydro-air. The moving air causes drafts and makes you feel cooler, which is fine in summer but not in winter. Also, the usual ductwork takes up a lot of space.

I'd use some sort of water-based heating. In-floor radiant is nice but expensive to install. You can also get many types of heat emitters that are placed in the rooms, from ordinary fin-tube baseboard to panel radiators, towel warmers or cast-iron baseboard.

If you really must have A/C, a mini-split or mini-duct system is the way to go. Mini-splits use small fan-coil units that serve one or two rooms, providing individualized control. Mini-duct systems use central fan-coil units but much smaller ductwork, with resulting higher air velocity that makes you more comfortable at higher air temperatures. They also take up less space.

You'll probably be living with your choices for a long time. Don't make your choices on price alone.

Gordy

I believe the duct work is in place? Maybe I miss understood that part?

If not yes I agree with @Steamhead hydronic solutions are much more comfortable, and efficient.

kcopp

I am in Seacoast NH.... I do HW systems only.
Seal it up well. and get a blower door test done.
That is the only way to know how well you did.

pfm

Thanks all for the quick replies. I really really wish NG was an option, but it is not and very unlikely to become one regardless of whether the Kinder Morgan proposed pipeline goes through. Ducts aren't a given except that we all have allergies with mild asthma; so, AC is very high on the wife's list. Agree on the insulation comment. Will have to take a closer look at the hydronic options. Anyone aware of any year-round operating cost comparatives against these options, Hybrid vs Hydronics?

JUGHNE

I have been around house construction since the mid 70's when there were a lot of new and great ideas thrown around for energy efficiency.
It is easy to stuff a wall with thick insulation and say this is great, but after the diminishing returns factor of thickness of insulation, what is often overlooked is the major heat loss factor of air infiltration.
Hopefully you have 2 full stories and not knee walls on the second floor. The issues of air infiltration are so subtle that they are easily overlooked. Every hole drilled, be it for cables or piping in every outside wall stud or every floor or ceiling plate needs to be sealed with caulking. Many GC's will say that this 6" of fiberglass takes care of that, I don't think so. The basement rim joist where the foundation meets the wood structure is another major leaker, again FG will not stop air infiltration IMO.
Every light fixture and outlet is another leaker. I have always installed a "mud ring" on ceiling lights, this requires a smaller hole cut in ceiling SR and as the fixture is installed the ring is pulled down tight to the back side of the SR, giving a tighter seal to the hole to the cold attic. ("But this is how we have done it for years and never had a problem") you will get for a response.
If possible install the required outlets on an inside wall near the corners, one perhaps rather than two holes would be in the outside walls. Recessed can lights are a major hole in the ceiling, even though the can says "IC" meaning you can bury it in insulation there is still plenty of attic air coming thru. Better cans "air tight" (a little more money) are available for tighter sealing. Or if possible that cans could end up in soffits better yet, as long as soffits are built after the ceiling SR is installed.

Exhaust fans are usually stuck in the ceiling with maybe the 4" piping run thru the roof, insulate the hell out of that exhaust pipe and still on a really cold day the condensation will run down and break the bulb in the fan/light. You have about a 1 foot square hole in your ceiling that is loose as a goose and then a 4" round pipe going thru the roof. Also wall sconces (if that is your wish) on an inside wall don't punch a hole thru the thermal envelope.

What I have done where possible and affordable is to put the bath exhaust fans in either an inside wall or build a soffit for ceiling mounting, and then run the exhaust down thru an inside wall ("what do you mean you want a 2 X 6 stub wall between the shower and WC....do you know how much that will cost us??")
Then vent the fans out the rim joists, never had any condensation issues that way. Same with the range hood, usually needs only a 2 X 4 wall with wall stack changing to 6" round in the basement and then again out the rim joists.

Every thing I mentioned above might not even add 2G to the costs. But it is really hard to change a GC unless he sees 1G in it for himself.


Any new structure of any substance built today should have to have some form of outside air introduced, heat exchanger or recovery, regardless of any codes. If the house is tight enough you will know that you need fresh air.

I would make a point to the GC that you intend to have a blower door test done and expect the results to be better than average by far. The problem is that after it is all finished it is very hard to correct things. But him realizing your awareness may ring a bell concerning details.

It sounds as if you are stuck with the forced air/ductwork. If so I would ask for the heat gain/loss print out the HVAC company come up with. Again your awareness will impress upon them that you know of such matters. Furnaces/AC's are just about always oversized, (I know--have the Tee shirt) this is not good for you. At best get a 2 stage gas furnace, the lower stage (maybe 60% of high fire) should heat your house most of the time. The high fire stage would be seldom used.

I will now put my soapbox away and let you absorb this if you wish.

Gordy

A method I have seen is foil backed drywall, gasketed openings with positive pressure in the house.

Fiberglass insulation is an air filter in my opinion. Dense pack cellulose.

njtommy

You could still run a hybrid system with hydro air. I do this in my own house. I run my heat pump down to 35 degrees the switch over to hydroair/ combi boiler.
You could also add radiant floor heat to the finished basement and first floor. Second floor could just run off hydroair if you either used zone dampers in duct work or added a second unit to the house.

Rich_49

Is the home to be built to the V2 Standard or VERIFIED to be V2 ?

If you are willing to make the investment to build the better house to hedge against future energy costs and to insure comfort maybe you need to be researching builders that are willing and able to build the house you desire .

Tankless water heaters are all marketing spin . When planning a new home and the systems an insulated tank type heater is best and can be used as the source for your wet heating system , whether it be air distribution hydronic emitters . These heaters cost roughly the same as garbage tankless , qualify for all programs that make sense (not scam programs , as many are ) . See the short video included in this discussion ,
http://forum.heatinghelp.com/discussion/156675/ng-supply-for-tankless-hwh#latest .

If you want renewables and want something that works and uses less energy than it's so called counterparts go with a Solar Thermal Drainback system with storage . If you must have a water / water heat pump also use a mixing valve on the storage tank to increase supply temp to the source side to 70* . This will boost the COP from the 4 range to the 7 - 8 range , it also eliminates the larger , energy hog pumps required with GSHP systems . Systems like this have SYSTEM COPs of GREATER than 10.
When the sun is not real viable for a week or more at a time your well built house can use that stored mass for weeks before it degrades to the point (temp) that you would run normally using GSHP systems .

Ducts should be reserved for Dedicated ventilation systems and not for space conditioning . Chances of finding a properly trained designer / installer of duct work is worse than finding a good Hydronic designer / installer . This smaller duct work can be located in other places as opposed to someone being required to insulate at the roof plane instead of the ceiling plane which we all know can be 2 -3 xs greater in area and require much more insulation . I always believed that bringing the attic into the thermal envelope was a waste just to allow one to place trash inside conditioned space .

I would suggest strongly in finding a builder who is intimately involved with building the type of house you REALLY WANT instead of the local guy who wants you over barrel and accepting what he wants to give you .

Henry

I have now 40 years in the hydronic, steam etc buisness, holder of three patents in combustion and heating plus a voting member of B149.1 and B149.2. So no bull regarding what is comfortable and efficient. In my house, I have a York fully modulating gas hot air furnace and a 3.5 ton dual stage AC. This talk about cold drafts from a hot air system is noncense. The Lennox is kept at low speed continuous fan to have even heating and cooling while at the same time have the electro/mechanical filter system control dog hair and odor. On a heat demand, the burner and fan modulate. High fan speed is only during cooling modes. In your case, I would recommend a Lennox system that would include a heat pump as your winter temperature are much warmer than ours up here. Proper duct design is critical. I had to ad return ducting to get things right in my house. Due to my allergies, I have to keep the windows closed and get to enjoy a filtered air year long. BTW, specially in heating mode, there is no noise from the system.

Brewbeer

Some really good posts above regarding getting the building envelop correctly sealed to minimize infiltration. This can't be overstated enough.

In southern NH, you will need heat between 200 and 240 days per year. You will need air conditioning between 30 and 60 days per year. This gives you an idea just how much more important the heating system is compared to the cooling system. If it were my house, I would install a hot water heating system, fin tube baseboard if you don't want to invest in radiant, with the emitters sized for 130 degree supply water temps. I would install a completely independent cooling system.

For a two story house, most of the heat load during the heating season is needed on the first floor, since the heat in the house will tend to naturally rise and keep the second floor warm. In the summer, the opposite is true; most of the cooling load is needed on the second floor, as the cool conditioned air will natural sink down to the first floor. I would also zone both the heating and cooling separately for each floor.

I just installed a hot water baseboard system in my 50 year old house and removed the forced air heating/cooling system because it was awful. It was so bad that I ditched the central air for window units (I might install a dedicated central air system in the future).

If you do decide to install a forced air heating system, I'd recommend these two things: (1) keep all the duct work inside the conditioned space of the house; e.g., no ducts in outside walls, and no equipment/ducts in the attic unless you build an enclosure for these components and insulate around the enclosure; and (2) read and understand these two sentences posted by Henry above:

Henry said:

Proper duct design is critical. I had to add return ducting to get things right in my house.

This illustrates that it is vastly more difficult to correctly design and install duct work for heat than it is for a hydronic piping system, and even then it may not have been done correctly. Hydronic piping is relatively forgiving; duct work is not. If you go the furnace route, make absolutely sure you have an expert design the system, make sure there are adequate returns everywhere (since you can't duct warm air into a closed room that doesn't also have return ducts), and make sure they show you all the calculations that go into the design.

Gordy

@Henry I applaud your accomplishments in the industry it needs more people like you.

I do not doubt the efficiency of your system in comfort, and economy.

But as @Rich pointed out it is much harder to find a tin knocker that can really super tune a forced air system, and duct work to give the benefits you point out in your own system. I'm sure you were the reason of its success.

On the other hand there is an unmatched comfort of neutral highly conductive floor surfaces that radiant floors offer, and or the feeling of liquid sunshine from a radiant ceiling when temps get down low.

Where hot water heating does trail is in the AC arena. You still need that part of the comfort system all though ducting can be a lot smaller than duct work covering two different seasons.

As @Brewbeer beer pointed out most of the load is heating in the OP's region.

As far as particulate control with filtration, and air movement. I have found a radiant conditioned home to be far less dusty than a forced air conditioned home. Just my personal experience pets or no pets. Bottom line most dust is from human dead skin, carpet fibers, outdoor,dust if summer with windows are open and if you have one pets.

All,dust,settles to the floor to be vaccumned away, or it can be airborne to be filtered away. I would rather have it settle as soon as possible than be airborne, and fill duct work before its filtered.

jMHO

BigRob

When your feet are warm, your body feels warmer. The comfort of a radiant system is pretty much unmatched and the ecm pumps are cheap to run. I've lived in both and the radiant floor is luxury. You will need to have the right floor coverings. Are you going carpet, tile, or carpet in the main areas? Radiant is best with tile with throw rugs. Wood works, but insulates more. If your exposure is good, solar thermal with a big tank for heating and DHW would be awesome. Maybe LP or geo for backup. As far as AC, you could install hydronic convectors for when it gets real cold and use them for AC when needed. There are a couple residential chillers from multiaqua and chilltrix that have heat pump options. Maybe that could be your backup heat and cooling? They also offer zonable exposed and hidden fan coils. Google it and see what you think. The individual room zoning and flexibility is impressive. If your power company offers tiered rates you could charge up the tank at off peak hours for both cooling and heating. As for insulation, I really like the Roxul mineral wool batts. They squeeze into the studs and are so much better that fiberglass. They seem to be better for noise, too.