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Space heating and cooling our homes – time for a rethink?

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One Step Off The Grid

At present, our conventional methods for domestic cooling and heating are generally directed at achieving a specified air temperature within rooms. We nearly always think in terms of ‘space’ heating/cooling but why do we do this?

These days, we commonly have large rooms in our houses which are often occupied by only one or two people – in these circumstances almost all of the energy we inject into our rooms is wasted since it is simply heating or cooling air in unoccupied areas of those spaces.

This almost total reliance on space, rather than ‘person’, heating is a relatively recent phenomenon. When I was a child in the 1950s I lived in a radiant heating world where the aim was to heat people not rooms.

The main heating in our house was a coal fire in our living room; we supplemented this with single bar electric heaters. We were warm on one side of our bodies and cold on the other; the house was smelly (and probably grimy) from fumes from the coal fire. I was very happy when the world moved on to space heating.

gas-heater

Now, 60 years on, we are in a very different place. Space heating, particularly of a whole house, but even of large rooms, is beginning to look like a high carbon option. Can ‘person’ heating make a comeback? Importantly, have technological developments now made radiant heating both comfortable and energy efficient?

Six months ago I was very much in the space heating camp (albeit at the room, not house, level), but over the past Canberra winter I’ve gone through a personal energy use epiphany. I’m now confident that we can successfully apply the old adage ‘heat people, not spaces’.

In 2015, as a key part of an energy makeover of our house, we installed Far Infrared (FIR) heating panels as a low energy alternative to heat pumps. We adopted FIR primarily because my wife said that the heat from heat pumps didn’t make her feel warm.

We installed two 1200W* FIR panels on the ceiling of our main living/kitchen space (see the photo below – this room has an area of about 45m2) at the end of last year’s heating season. When we installed the panels I was still very much in space heating mode – I figured that we would use the panels in a way that would keep the room warm; and by default we would be warm.

However, at the start of winter 2016 I soon discovered that the two FIR panels could work independently and that you didn’t have to have the room warm to enjoy beautiful thermal comfort. When I was sitting under one panel it felt no different whether the other panel was on or off.

On realising this, we of course only turned on a panel when someone was sitting under it – we made no attempt to warm the room. While I was sitting under a panel enjoying lovely warmth (around 20-22⁰C) on a cold Canberra evening, just a few metres away the temperature in one corner of the room was often around 12⁰C. I rapidly became a ‘person’, not ‘space’, heating convert!

screen-shot-2016-10-11-at-2-55-30-pm

I have written a more complete report on our FIR experience, but in summary I call the areas under the FIR panels thermal islands. I

estimate that even on a cold night one person would be able to attain beautiful thermal comfort under a panel which has dimensions of around 600mm X 600mm and a power output of about 400W. In the case of our living/kitchen area, this energy use compares to an estimated 4kW of heating that would be required if we were space heating the room.

Discovering the beauties of FIR soon had me thinking about what the next generation of domestic heating might look like. Given how discrete the FIR thermal islands are, it is not too hard to envisage the whole ceiling of a room being made up of a mosaic of 400W FIR panels – this would enable each individual in a room to turn on their own thermal island and select a temperature which suits their needs.  In fact, FIR panels of these dimensions are now being made as tiles for suspended ceilings.

infrared-heating

Of course, in practice, the energy gains of personal, rather than space, heating are not clear cut. With one person in a large room you will almost certainly use less energy by heating with FIR than you would using a heat pump. However, as the number of room occupants increases, or the size of the room decreases, the energy use/person balance between the two heating options is likely to change in favour of space heating.

It is all very well to dwell on heating, but for most regions in Australia cooling is the major energy use for a household. As climate change progresses this is likely to be even more so. I am now starting to turn my mind to ‘person’ cooling as summer 2016/17 approaches. On the face of it, it would appear to be much more difficult to create multiple zones of user designed cooling, rather than heating, within a room.  I’ve not explored this too far as yet, but just as FIR opens up a world of ‘person’ heating I like to think that Li-ion batteries will give us a corresponding ‘person’ cooling option.

Ultimately new battery technology may enable us to each carry around some form of personal refrigeration. In the meantime, my start is much humbler and lower energy. There are now quite a lot of rechargeable fans on the market which are primarily designed for campers. I am currently in the process of acquiring a 6” rechargeable fan (weight 1kg) and intend to use this as a movable personal fan throughout our house. I see the untethering of fans from electrical cords and plugs as being a major boost to the practicality of using a personal fan within a house (I’m talking about an effective personal fan; not one of the very small ‘toy’ hand held fans that have been around for years).

It remains to be seen how effective this option will be compared to air conditioning. However, if this idea seems attractive but not cool enough, you may wish to keep an eye on a portable rechargeable air conditioner that is currently under development.

Dave Southgate retired from the public service in July 2012 after a 31 year career as an environmental specialist in the Australian Government Transport Department and then as the Australian Government representative on the United Nations International Civil Aviation Organization (ICAO) Committee on Aviation Environmental Protection (CAEP). Since his retirement he has expanded his climate change interests and has become fascinated with renewable energy.

See also: A journey to fossil fuel freedom – no heat pumps required

This article was originally published on RE sister site, One Step Off The Grid. To sign up for the weekly newsletter, click here

A previous version of this story said “We installed two 1200kW FIR panels on the ceiling…” The mistake was made by the subeditor.  

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  • Rod

    Agreed, for singles and couples personal heating makes sense. How about a couch warmer? Cars have seat warmers!

    As for personal cooling: I understand comfort in Summer with no air movement is around 21C but with air movement is 27C.
    We set the AC to 27C and use standing fans on the very odd occasion when fans alone won’t do.
    I agree the cables running everywhere are a bit of a pain and rechargeable portable fans would be better.

  • Brunel

    We can have room heating or floor heating but not by burning gas.

    Heat pumps are cheaper to run.

  • Tim Forcey

    Join in the discussion about using heat pumps and other heating means at “My Efficient Electric Home” on Facebook. https://www.facebook.com/groups/996387660405677/

  • Thanks for your write-up Dave. I looked into FIR panels earlier this year, thinking they might be very handy in the bathroom, but wondered if they really were as effective as made out. I didn’t go ahead with buying one at the time, but might consider one for next winter.

    • Tim Forcey

      HI Gordon. Most bathrooms could go for an “Ecotastic”. http://ixlappliances.com.au/product-details/eco-tastic/12343

      • Thanks Tim, my parents old place had one of them in the bathroom, but they are a bit much of a power guzzler for me, being off-grid. A 600W FIR panel should be sufficient, the bathroom is only about 8m^2 floor area, and we have an exhaust fan in there already.

      • Alastair Leith

        Hi Tim. And there’s that shower dome I’ve heard good reports on. Not so good if you’re taking a bath of course.

    • dave southgate

      Hi Gordon. I’m not sure my FIR panels would work all that well in a bathroom – I think the heat would be a bit too subtle. I recall the guy I bought my panels from talking about special panels for bathrooms – if you want to follow it up you may wish to make contact via http://www.heat-on.com.au/.

      • Way ahead of you Dave 🙂 Back in Feb I spoke with Paul T from Heat-on, and he reckons it would be fine. He is also off-grid and uses them in home.

  • Ian

    Love the idea of personal cooling. The best way to achieve this is with approximately 300 to 500 ml of personal-coolant. This can be carried in special aluminium cans and the cold temperature maintained using neoprene foam sleeves. The coolant is taken by mouth and directly cools the individual from inside. Frequent visits to the insulated storage facility can replenish the coolant. Three issues with this method of cooling are fights erupting over the last container of coolant, occasional loss of consciousness from excessive cooling requirement and the rupture of the usual urinary seal requiring disequilibrium movements to the nearest toilet.

  • MaxG

    What a bunch of bull! Stick insulation in new homes… we are building a 10 star, actually passive house… requiring 2.5kWh of energy per coldest or hottest day… we will have a comfy 22 deg C in winter and 24 deg C in summer… and energy to spare. (Location 100km west of Brisbane 200m AMSL)… at this level of energy requirement. I happily heat the whole house… in fact, our body heat will heat a normal sized room (~9m2)

    • Ian

      Max-G’s, I wouldn’t go so far as to completely discount the writer’s suggestion for radiant heating or cooling. It has a lot of merit. You are of course right about insulation as being the primary requirement for good home environment conditioning.

      But when you think about it, air has a very low thermal mass and in a room with no mechanical circulation conduction and convection have a very small role to play. Heat transfer from or to the person is thus predominantly by radiation. Floor, walls, ceiling and furniture either act as warm bodies radiating heat or reflective bodies reflecting heat.

      • Ian

        Here is a thought-experiment: If you had an empty room with mirror like walls, ceilings, and floors and had a small radiant heater in one corner of the room. A person could stand in any part of the room and experience full heat transfer from that heater. The infrared radiation would just bounce off all the surfaces of the room until it encountered a relatively heat-absorbent body like that person in the room. Now add some furniture to the room all light weight and with low thermal mass with surfaces that are part absorptive and part reflective of infrared radiation. These would quickly heat up to a comfortable temperature similar to the body heat of the person in the room and ‘ disappear’ as it were. Now make the room surfaces partly absorbent and partly reflective, make them very thin and back them up with perfect insulation. Again, like the furniture the thermal mass of the walls, floor, ceiling is small, rapidly approaches that of the person in the room and again disappears from the heat transfer equation. All that is left is the reflection of heat from the radiator and the absorption of heat by the human subject.

        So max, plenty of good insulation all around the room and a small radiant heater is all you need to keep warm anywhere in that room.

      • MaxG

        There is the problem: a room w/o mechanical ventilation — implies the building is leaking, otherwise, the better insulated (and this includes air0tighness) the more ventilation is required to remove CO2 and provide oxygen to the occupants. I still believe, the radiant heat is a band aid and not the solution to the root cause of current (faulty) building technology.

        • dave southgate

          I think you’ve hit on one of the major advantages of FIR heating. For space heating to be effective you need to have very well insulated and well-sealed rooms. As you say this then brings in the imperative for mechanical ventilation – more energy use; more complexity. If this is not set up correctly, or fails, you have indoor air quality problems. With FIR in a ‘people’ heating mode the heating effect is more or less independent of the level of building insulation – much simpler building design; much better indoor air quality.

          • MaxG

            Anything that is not set-up correctly is not an issue of complexity, but incorrect maintenance.
            You will find that a well-insulated house will out-perform any normal house by miles — or should I say by dollars 🙂

          • Ian

            Actually, with a well sealed and insulated room, heat will radiate around the room to all objects within it, you don’t need to rely on convection to transmit the heat.

        • Ian

          Here’s the thing, air weighs roughly 1.2 kg per m3 and the co2 in it 0.7 grams a human will produce roughly 900g of co2 in a day. So a person sealed in a room 20m3 will raise the co2 level from next to nothing to .9/(1.2 x 20) = 3% co2 in a whole day roughly the co2 concentration exhaled in a single breath. The point is you won’t run out of oxygen or choke on carbon dioxide if a house is well sealed. Leaving a couple of small openings in the house envelop will probably allow enough air exchange through diffusion to keep the place from becoming too stuffy. You wouldn’t need extractor fans to exchange air . Interestingly the bigger the room, the less air changes are needed to keep the occupants comfortable. So a large well insulated room with thin dry walls and a relatively small heater of any type is probably better than a small well insulted room needing frequent air changes.

  • solarguy

    We have split reverse cycle AC’s in our house, one room, ( whole room) 20sqm can heated or cooled for energy use of 2kwh over 5hrs. That’s 400w for every hour at a setting of 23c
    I rest my case.

  • >>, you may wish to keep an eye on a portable rechargeable air conditioner that is currently under development.

    uh oh… unless the makers of this little device have found a way to break the Laws of Thermodynamics, it’s not going to work as claimed in that story (and the included photos are a joke!), unless of course there is a tiny superinsulated compartment inside the box where all the heat goes, at blast furnace like temperatures!
    The heat removed from the air has to go somewhere, and in the absence of a duct to remove the hot air, it can’t possibly work to cool a closed room. Maybe if you sit in front of it a cool breeze is possible, but the rest of the room is going to get hot- so a cool face while the rest of you sweats buckets.
    A 4.5m square room is tiny, but lets say it is 2.4m high- that’s a bit over 10m^3 of volume, which they claim that can cool to 6C. A commercial refrigerator to operate at 4C of that size probably has a 1HP or larger compressor, so what kind of battery is in that box to power that sort of compressor for more than a few minutes?

    I think I’ll give their kickstarter campaign a miss!

    • dave southgate

      If you look in the pages at https://www.indiegogo.com/projects/zero-breeze-the-world-s-coolest-portable-ac-unit#/ you’ll find they have a exhaust pipe arrangement for indoor use – you simply stick the thing out of the nearest window.
      I guess it will work but I’m sure it will make it much less easy to move around a house than my small rechargeable fan.

      • Gizmodo have it wrong then:

        >>Unlike the portable air conditioner sitting in the corner of your
        bedroom that requires an exhaust vent, an outlet and a bucket for
        catching drips, the Zero Breeze is as compact as a boombox and can run for up to five hours on its own rechargeable battery.

        I wonder why they think it will be any different to any other portable AC? We were given one (since disposed of as useless), and whilst it was cool if you sat in front of it, it guzzled a lot of power, around 1600W when it was hot (it was rated 850W). We decided it really didn’t do much more useful cooling than the 30W DC fan we now have!

  • Ben Davies

    The main downside of these German-made FIR panels is the cost. I could almost get through a years worth of electricity for the cost of one of those.

    Far better the seal the house especially if it is an old wooden one like mine and then insulate. Passive is the way to go.

    • Ian

      Do you really think so, that sealing a house is better than insulating it? If your old wooden house has a low thermal mass then you would be relying on the house envelop to keep the heat ( or cold) in. Obviously having all the windows and doors open would result in very rapid air turnover. But consider a house like yours having all large windows and doors shut and a few leaky cracks and gaps. Would that house be better upgraded by sealing every little crack and crevice or by insulating all walls, ceilings and floors with lots of pink batts?

      All I can say is that I put pink batts in every available external wall and in the ceiling and under the colourbond roof. We hardly use heating or cooling and are not particularly careful about keeping the windows shut. We do live in coastal SouthEast Queensland so pleasant year round ambient temperatures probably has a lot to do with this!

  • John P

    My reverse brick veneer place in rural Victoria uses no heating or cooling appliance.
    It collects waste heat in summer and stores it in the brickwork until the external temperature drops low enough to allow it to leak out into the house. This heat keeps us comfortable through the winter.

    • Ian

      The idea of using a large thermal mass in the house, insulated on the outside is not a bad one. This type of home environment conditioning assumes that the ground source temperature from the floor linked to the earth and the average daily temperature between day and night fall into the usual human comfort zone. If the thick walls and floor of the house stay at a nice temperature all year round then one doesn’t need to have a very rigorous air-tightness to the house.

      In fact a very thick brick or rammed earth or concrete wall would conduct heat slowly. If the sun were to heat the outside of such a wall the heat would take all day to reach the inner surface of the wall and the evening cold would take all night to extract the heat again. So, no insulation would be required.

      From what I can gather Australian houses are generally designed to have a low thermal mass so that not much heating or cooling is wasted on heating the walls and floors. You wonder how these two diametrically opposed ideas can be combined in one house.

  • Diego Matter

    “While I was sitting under a panel enjoying lovely warmth (around 20-22⁰C) on a cold Canberra evening, just a few metres away the temperature in one corner of the room was often around 12⁰C.”

    Be careful: This could lead to future condensation problem at this very corner.

    If surfaces cool below the condensation point moisture problems start to form. the condensation could form inside the wall and rot wood because the inside of the wall would be even colder and prone to condensation.