Hydronic vs. Hot Air Furnace using Natural Gas

Chris Mudd

We are building a new home in Maryland and are trying to decide what type of HVAC system to go with. We will install Central AC, so duct work is required no matter what the decision. We will use natural gas for heat and hot water.

Energy efficiency is very important to us, as long as it pays for itself over time.

The dilema is a three zone (which requires three furnaces) gas furnace system vs. a zoned hydronic baseboard system.

It seems that the equipment and installation costs of three high efficiency furnaces (+ hot water heater) are still much less than a high efficiency boiler with the piping and baseboard systems.

Is hydronic heat more efficient than baseboard? Is it worth the added expense?

As you know - gas prices have been on the rise and neighbors tell us they had bills of $500/month last winter.

Any thoughts?

Thanks,

Chris

hr

Mix it up

consider a boiler or boilers as your heat source. Then you can blend some radiant floors into the mix for bath, kitchen or other hard surfaced areas. Hydro air and baseboard or panel radiators can be blended in also.

I've been in denial for years but today homes really need some air movement, conditioning and often HVR units to assure a healthy condition inside the home.

Controlling moisture levels is the key to hardwood flooring and wood furniture. That's hard to do with just a hydronic system in todays tight homes. You need to be able to add or remove moisture as required.

You should find a contractor that can design a system that provides the best indoor comfort, and mix and match the best components.

A heat loss and heat gain design is a MUST first step. Don't hire a contractor that stabs in the dark on design and sizing

hot rod

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Carl PE

This isn't going to make me very popular..

You don't actually need 3 furnaces. Trane and Carrier (and probably a few others) make a furnace with a variable-speed blower and a zone damper setup. Obviously, it's more $ than a regular furnace, but not as much as 3.

There are numerous posts here regarding relative efficiencies/advantages of air vs. water systems you should probably review. I'm not going to throw any more gas on that fire.

Carl

Ranger

absolutely agree...

...with hotrod.And I would add that I would look harder at being comforable In my own home more than payback as far as
up front expenses.The "payback" is in the enjoyment of your indoor environment.

GMcD

Whole building approach

Have you done a "whole building" approach? My advice is to spend as much as possible on the envelope (glass especially) to minimize the heating and cooling requirements in the first place, thus minimizing your on-going energy consumption no matter what mechanical system you eventually decide on. That means reducing solar gain and cooling loads in the summer by exterior shading, window tints, etc. and minimizing heat losses in the winter by high thermal performance glazing. Then all of a sudden the perceived "need" for zoning and perimeter vs interior control is minimized.

The most energy efficient HVAC systems are hydronic (water based) and I would suggest consideration of radiant heating and cooling, with an HRV that also can be equipped with re-heat/re-cool coils on the supply air ducts for sub-zoning. Consider a geothermal heat pump unit that can produce both heating and cooling as required. The costs for geothermal can be minimized by making sure the heating and cooling loads of the house are minimized in the first place by the high performance envelope.

There are a variety of radiant approaches: Karo capillary tubes embedded in ceilings (radiant heating and cooling from the ceiling), or the conventional floor system which can also provide a bit of radiant cooling as long as the cooling system temperatures are kept above the dewpoint. If dehumidification is needed in the summer, do it through the HRV with a dessicant system or a small split system refrigerant coil and outdoor condensing unit. The right approach is to look at the whoole building costs and energy requirements before the footings go in to balance the capital costs against energy perfromance and best-fit HVAC system options. The best bang for the buck will be found by long term passive energy reductions via the envelope.