Overheating – over here or over-hyped?

There have been a number of studies on domestic overheating carried out in the Uk recently, and a lot of anecdotal evidence that new homes overheat significantly. The anecdotal evidence from clients is that it particularly affects new apartment blocks designed with communal heating systems. The design of the fabric did not take into account the considerable losses of heat from the hot water distribution systems, and this ‘spare’ heat has significantly overheated communal spaces. In some cases corridor fire doors are propped open to all for ventilation.

This does not sound good. Particularly given that we can reasonable expect warmer summers to become ‘normal’ over the lifetime of these buildings, and there are many documented cases of ‘heat death’ occurring during these warmer summers. How long will it be I wonder before some civil suit arises, blaming building designers for overheating?

The defense that will be offered is that the compliance tools in this area are woeful, inadequate and inaccurate, and that there are no effective standards governing this. Recent work by the Zero Carbon Hub on the subject demonstrates the disparity between the overheating estimates produced by SAP, PHPP and IES. In round terms the scores are PHPP (0) SAP(1) and IES and other dynamic simulation tools (5). The reality is that only a dynamic simulation package can reasonably estimate overheating because it is a problem of dynamic physics played out over time and not one of totals that can be calculated annually. The problem is that few if any of the major housebuilders consider this in their housetype design and few residential designers in the sector are familiar with this complex problem.

As we design homes to ever tighter airtightness, and focus on carbon emission savings, we are in danger of losing sight of the importance of human comfort. Overheating in such homes is a symptom of this focus and one I will come back to in the near future when I discuss our work with VELUX on their demonstration project in Kettering.

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7 thoughts on “Overheating – over here or over-hyped?

  1. Great piece Rory. I am obsessive about this topic. I have carried out a lot of thermal transient analysis in the nuclear and power industries and my recent intro to the building industry leaves me shocked at the lamentable understanding of heat. It seems to me we are heading for some horrid new buildings. BTW the wattbox controller would reduce that heat loss from hot water systems as it avoids the excessive water heating which is common with standard controls. I would appreciate a contact if you know someone with a specific problem. Thanks

    • Hi Jim, thanks for this, can you go into a bit more detail about how the Wattbox might work with a communal heating system. Do you need a hot water store in each apartment to make this type of control work? Isn’t the main problem with communal systems the heat losses in the distribution system which are outside the control of the domestic system?

  2. Pingback: Overheating | DemandSideSolutions

  3. Thanks Rory,

    The Wattbox controller learns the behaviour consumption patterns of the “house holders” and builds an automatic time profile and temperature profile to suit the leant consumption pattern. It does this for space heating and also hot water consumption patterns. This is much smarter than a house holder trying to remember/guess the correct start and stop timings. The controller has primarily been developed for domestic houses (space heating and hot water) but we are starting to think about how it can be used in commercial/larger buildings. In the communal heating case you mention it would learn the hot water consumption patterns of the users and only store the right amount of hot water to meet their needs and no more. In practice this means hot water tanks are held at lower temperatures and boilers are cycling less to maintain that heat.

    For example in my house using the old 7 day timer the only timings which I could get to work for the family were to keep the tank fully hot pretty much 24/7. Now we have fitted the Wattbox controller it has leant that we require enough for about 2 small showers in the morning and a bath at night but only on certain days. Having worked this out it then does the maths to accurately determine the best start time and then stops heating water when the temperature sensor gets to the “learnt” temperature. By learning this, the tank, in practice, is about half hot during the day time and also night time (when we do not need much hot water storing) and the boiler spends little time cycling to keep the tank fully hot. This has made the airing cupboard upstairs much cooler and the reduced boiler cycling also saves on pipe-work heat losses. This reduction in leaked heat would work in a communal system assuming there is a valve which can be closed when the tank has enough stored heat. If there is no valve or pump to open/close then the system is out of control anyway and you need fit a valve/ pumps for any control system to have a chance.

    In summary, I think this all works in a communal system as in practice users do not need a fully hot tank all the time, but it is beyond their humans skill to time a programmer with the required level of accuracy and then modify and optimize it continually as our advanced control system can. So we put the brains into a silicon chip (its that easy). Shout if that not clear or have a look at http://www.wattbox.com and then shout!.

  4. Thanks Jim, thats pretty comprehensive!. I think that the points you make are all good ones and I hear that commercialization of your system has started, congratulations. I can see how this will help to reduce overheating in each individual home, which is a big step forward. There remains a problem in dense apartment buildings where high temperature hot water is circulating in the heat distribution network outside the apartment in the hallways and risers, and there is no obvious way to reduce the heat losses from them, except by better insulation measures.

  5. Yes Rory, I was afraid you might say the hot water is endlessly recirculating. Brings me back to my initial point that the building industry doesn’t seem to understand heat or just wanted a cheap building from day one.
    The only other thought we had is if you can reduce the control temperature of the distribution system. Building managers may like it at 65C but 50C will give a very good result in summer months, and would reduce the heat loss to an external ambient of 20C by 33% (1-30/45=33%. This is cheap if the controls can be sorted.

  6. Pingback: Communal versus Individual Energy and Heating « RoryBergin’s Blog

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