Hydronic Heating Explained

by Chris Lang on November 24, 2011

Hydronic Heating

One of the most energy consuming aspects of any home is in making the inside temperature comfortably constant in spite of the prevailing weather conditions outside. On average, Australian homes consume 63 percent of their overall energy use on space heating and cooling, and heating domestic hot water (according to Your Home website). There are many space heating systems available on the market today, some more energy efficient than others. Here, we talk about one system that is growing in popularity in Australia and is considered the gold standard for homes in Europe – hydronic heating.

Hydronic heating involves heating water, and then circulating it to every room that requires heating. The central component of this heating system is the heat exchange unit. This unit holds hot water ready for it to be circulated through heating pipes or radiators, and receives hot water from a boiler and potentially a solar hot water system. The heat exchange unit can also include an outlet for domestic hot water.

Heat is radiated into a room typically in either of two ways: through pipes set under the surface of the floor, or through a series of radiators.

Under Floor Heating

Hydronic heating pipes can either be laid on top of reinforcing prior to a concrete slab floor being poured, or laid on an existing floor and covered with a concrete screed (poured as a standard concrete mix or using a self levelling screed). These pipes are laid as coils, one for each room, and connected to a central manifold. This manifold feeds hot water from the heat exchange unit.

Hydronic Heating Manifold

In-slab hydronic heating appealed to us because of the penetrating and gentle warmth it gives, and the 180W required to run the circulation pumps could be accommodated by our solar and wind generation system. Electrical energy is precious as we are not connected to the electricity grid.

Radiators

Discrete radiator units can be fitted to homes where under floor access is not feasible. Hot water and return water pipe loops are sometimes installed to distribute hot water to each room. Where hydronic heating is retrofitted to an existing building, pipe work can be integrated into a custom skirting board making it less obtrusive.

Heating the Water

There are plenty of options for heating the water required for a hydronic heating system, and my recommendation would be to have a boiler that uses the cheapest form of energy available to you. In most urban settings, a natural gas boiler would make sense, where as in a rural setting where plenty of timber is available, a wood-fired boiler may be more cost effective. I have also heard of boilers being run from other energy sources like briquettes, oil and LPG. You can supplement the heat from these boilers with a solar hot water system too.

But it is worthwhile keeping in mind that solar hot water will only contribute to part of the heat required to run a hydronic heating system. As an example, our 180 square metre home requires around about 27kW of energy to heat during the depths of winter (our home is in western Gippsland at the foothills of the Strzelecki Ranges). Around 7kW (or 26 percent) of this energy is provided through 60 evacuated solar tubes mounted on our north facing roof. The rest is supplied through our wood-fired boiler. Although, timber is in plentiful supply at the moment, our long-term plan is to plant a wood lot to harvest timber for our wood-fired boiler, thus making our system truly sustainable.

Hydronic Heating Manifold

Cost

As a guide, here is a breakdown of our costs to supply and install a hydronic heating system in our 180 square metre home:

  • In slab heating pipes (PEX-A specification) and manifold $6,500
  • Famar Brevetti wood fired boiler (rated to produce just over 20kW of heat) $7,500
  • Heat exchange tank (900 litres), circulation pumps, and 60 x evacuated solar tubes $7000 (inc works to connect all parts together and commission).

My advice in working out rough costs for such a system would be to firstly understand the approximate floor area that you need to heat. Next, decide on the fuel that you will use to heat water in your system. Do you want the system to supply domestic hot water? Do you want heat in the system topped up with solar hot water? Armed with this information, jump on the phone and get some quotes. You should find that having a clearer idea of what you want would get you better estimates.

The Results

The design features of our home and the thermal mass of our concrete slab floor contribute significantly to maintaining a stable temperature inside our home. Without any active heating or cooling the inside temperature of our home ranges from 15 to 26 degrees (experienced in the middle of the 46 degree heatwave Victoria experienced in early 2009). When we run our wood-fired boiler in the middle of winter, we use around a wheelbarrow of timber a night, and this keeps the temperature of our main living areas at a cosy 21 degrees. Moreover, there is nothing better on a cold winter’s day than walking around on toasty warm concrete.

This article was written by Luke Potter – a writer and commentator on sustainable building and living techniques. Need more information? At www.budgereehouse.com, you will find more information on how to design, prepare for, install and operate your own hydronic heating system. In addition, you can contact Luke Potter directly with any specific questions at [email protected]

{ 3 comments… read them below or add one }

Greg Phillips June 15, 2016 at 11:19 pm

Hey Chris, thank you for taking some time out and creating such a good post explain hydronic heating systems. Keep posting such good contents.

Reply

kroll heat July 15, 2016 at 10:59 pm

Great post Chris. But I would recommend you to put some flow chart while explaining the working of a hydronic heating systems. I think it would be more helpful to readers searching for hydronic system’s working.

Reply

John Burke September 14, 2016 at 5:55 am

Hi Chris,
I notice that the red and blue manifold are by SBK.
Would you know of a supplier that could supply wireless thermostats and compatible actuaries for the SPK manifold, the tread on the manifold is 30 x 1.5 mm ?
Regards
John

Reply

Cancel reply

Leave a Comment

Previous post:

Next post: