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Green Building Bible, Fourth Edition
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  1.  
    I've just had a very depressing meeting about a new school. Many issues, but they say they have no budget for an air source heat pump, so will use gas. I also asked about UFH. They practically laughed at me and said it was totally unsuitable for a school as it takes too long to heat up and cool down. I can possibly see the issue with cooling (many people in a hall, say), but surely there are ways around this? Does anybody else agree that it's a problem in schools? From a quick google, there seem to be many companies offering it.
    •  
      CommentAuthordjh
    • CommentTimeDec 10th 2019
     
    I'm not surprised about the attitude, since that was my first reaction knowing nothing about the subject. I agree there do seem to be products and installations out there. I haven't read enough to form a view on whether they are sensible or not.

    If you want to pursue it, you seem to have a two-fold agenda:
    (1) find enough independent evidence and support to prepare a justifiable first sketch design and cost it, and
    (2) figure out how to finance it.

    (2) I expect depends on what type of school it is and how it is funded. But for example councils can now borrow government money for commercial investment, so maybe some council would be able to provide a loan? (assuming the numbers make sense, of course).

    (1) comes in two parts, the energy source and the heat distribution mechanism. You should at least try to persuade them to plan to allow for an ASHP or GSHP to be fitted at a later date, with suitable emitters either fitted or upgradeable later. What are their current plans?
  2.  
    Thanks @djh. It's developer funded, I think about £10M, so I don't think there is any flexibility. I do get the impression that the builder is trying to deliver the absolute minimum. There are loads of other aspects where they haven't considered the environment whatsoever. I don't think they have any plans, other than making as much profit as possible.
    •  
      CommentAuthordjh
    • CommentTimeDec 10th 2019
     
    Who's the client? (or type of client if you'd rather not be explicit)
    • CommentAuthortony
    • CommentTimeDec 10th 2019
     
    Reactionary springs to mind, what is the design life of the school?

    Target U values of walls floors and ceilings ?
    • CommentAuthorbarney
    • CommentTimeDec 11th 2019
     
    UFH will work well in schools - but you need to be very careful about the floor temperature if it's a primary or SEN capability

    ASHP in heating only are perfectly viable, a small cooling coil added to the mech vent in the hall etc would deal with any overheating risk (if the building is designed to avoid overheating) - run that again from a heat recovery ASHP

    Plenty of roof area for PV and it provides a revenue stream for the school as well.

    If this is developer led, then don't expect any of the above - but you could lever some change if you get BREEAM excellent in the planning conditions.

    Regards

    Barney
    • CommentAuthortony
    • CommentTimeDec 11th 2019
     
    In a well designed school the pupils should provide enough heat to keep their classroom warm.
    • CommentAuthorbarney
    • CommentTimeDec 11th 2019
     
    LoL - but they are often not present in the classroom, Tony - weekends, evenings and school hols tend to get in the way of that philosophy.

    Also the teachers don't like being cold !!

    I'm guessing you don't design many schools, do you

    Regards

    Barney
    •  
      CommentAuthordjh
    • CommentTimeDec 11th 2019 edited
     
    https://www.passivhaustrust.org.uk/news/detail/?nId=675 is perhaps a realistic aspiration, though probably not for ComeOnPilgrim's example. :cry:

    To be fair, if there's nobody in a school, there's not much point heating it except above frost danger. But I'm sure there are frequent occasions when there are people present but not the full complement.
  3.  
    Kids are in school for 6 hours of each weekday in term, so less than 15% of the overall time. Teachers for 9 hours. Otherwise there's nobody there but the stick insects. Each room has sudden changes of occupancy, from zero to 30 kids at 9am Monday morning, and vv at lunchtime, so needs either lots of thermal mass or rapidly responsive heating.

    Barney's given the pro advice, just to add that our local council procures all the new school buildings from a panel of developers through a Scotland-wide programme. This involves lots of multi-project type specification documents that are used for 100+ schools. Typically they specify what temperature they want the different rooms to be and how much they want to pay for heating. The developers then make bids in which they propose how they will design and heat the building. If they can save money vs the spec, their bid gets extra score. Once the process is done and the project is awarded to a developer, it's very hard for the council to come back and say they want it heated or insulated differently. CoP, is there a similar process where you are, can you influence the project specs before bid?
    • CommentAuthormattstan51
    • CommentTimeDec 14th 2019
     
    I've worked on schools professionally for nearly 30 years.

    The problem with underfloor heating is recovery time

    In many schools the doors are open for long periods; inside outside play, queuing for lunch etc.

    Underfloor heating just didn't recover quickly enough in these situations

    Also as said before for SEN or doesn't work as the floor gets too hot to be comfortable
    •  
      CommentAuthordjh
    • CommentTimeDec 15th 2019
     
    Posted By: WillInAberdeenso needs either lots of thermal mass or rapidly responsive heating.

    I believe the thing to think about is response times. Lots of insulation slows response times, so both the quantity of thermal mass and the responsiveness of the heating become less important. In our house I'm still quite happy heating it overnight (E7) and letting it coast through the day, as one example. Typical temperature excursions are half or one degree, unless it's sunny all day when we benefit somewhat more.

    I don't doubt schools (and offices and all other types) have specific patterns and problems and benefit from specific design considerations and solutions. My brother was involved in designing a few. Ventilation is another major feature.
    •  
      CommentAuthordjh
    • CommentTimeDec 15th 2019
     
    Posted By: mattstan51Also as said before for SEN or doesn't work as the floor gets too hot to be comfortable

    Floor temperature again is a consequence of the [lack of] insulation. In a well-insulated building floor temperatures only need to be a degree or so higher than air temperature to provide the desired heating.
    • CommentAuthortony
    • CommentTimeDec 15th 2019
     
    Leaving or having doors open during the heating season needs to become a thing of the past
    •  
      CommentAuthordjh
    • CommentTimeDec 15th 2019
     
    Posted By: tonyLeaving or having doors open during the heating season needs to become a thing of the past

    TBH I don't worry about it as long as it's not for too long or too wide. It depends a bit how windy it is but sunny cold and still means I'm probably gaining as much from the sun as I'm losing through a door open one cat-width, for example. Or at least that's my unscientific guess.

    But shops for sure need to educate customers to expect doors to be closed in winter (and educate themselves if they don't understand why).
  4.  
    Posted By: djh
    Posted By: WillInAberdeenso needs either lots of thermal mass or rapidly responsive heating.
    Lots of insulation slows response times, so both the quantity of thermal mass and the responsiveness of the heating become less important.


    Mmm, I don't really follow that. Insulation will slow down the rate of cooling, but has no effect on speed of response to heating.

    Imagine a classroom at a comfortable temperature at 0859 Monday morning. The heating is working at a rate to exactly balance the heat losses. Then 25 people walk in and turn on the lights and IT, adding say 3kW of body heat to the room. Either the heating system has to instantly reduce output by 3kW, or the fabric has to absorb an extra 3kW without heating up much, or else everyone overheats and opens the windows. Adding insulation will not change any of this, though it would mean the building stays warmer for longer when everyone has gone home.

    Our kids' school has a Victorian granite building (lots of thermal mass, big radiators) and a 1990s prefab unit (very little thermal mass, responsive electric fan heaters). Neither have much insulation that I can see, but both keep pretty stable temperature in their ways.

    Now ideally there'd be more insulation, so less heating needed over the weekend, so less ability to turn down the heating by 3kW at 0900, so more thermal mass would be needed, maybe more expensive to build. More thermal mass would support slower-responding heating systems such as ashp+ ufh.
    • CommentAuthorgyrogear
    • CommentTimeDec 16th 2019
     
    totally off-subject,; but where's the windows in all of this, and will the Low-E be installed the right or the wrong way round ?

    gg
    • CommentAuthorSimon Still
    • CommentTimeDec 16th 2019 edited
     
    Posted By: WillInAberdeenImagine a classroom at a comfortable temperature at 0859 Monday morning. The heating is working at a rate to exactly balance the heat losses. Then 25 people walk in and turn on the lights and IT, adding say 3kW of body heat to the room. Either the heating system has to instantly reduce output by 3kW, or the fabric has to absorb an extra 3kW without heating up much, or else everyone overheats and opens the windows.



    I'm probably not going to explain this very well, but in a very well insulated building you can run underfloor heating constantly (rather than cycling on and off) at very close to the room temperature (varying the flow temperature based on the external temperature to balance losses with inputs).

    If your target temperature is 21C and the floor is only running at 24 or 25C then if the room temperature increases due to all the students arriving the heat transfer from the floor rapidly decreases. The room might rise a degree or two but not so that it's uncomfortable (and you might make the target temp for an unoccupied room 19 or 20C as a result).
  5.  
    Yes, that's where I was going last paragraph.... (nicely explained Simon!) . Running the ufh at that temperature (so giving ~20W/m2 output) would put ~1kW heat into a 50m2 classroom, which might be enough. Adding ~3kW of body heat would require the 1kW heating to quickly become 2kW of cooling, need to let the thermal mass absorb some of that.

    But observed on the school run today: the heating does need enough oomph to cope with several sets of double doors being propped open in mid December to let everyone out! Probably couldn't boost the UFH temp to get enough kWs out to respond to that quickly.

    Edit to add: an air-to-air heat pump or air-con system would be a good solution, probably more responsive, efficient and cheaper than ufh.
    • CommentAuthorSimon Still
    • CommentTimeDec 17th 2019 edited
     
    Posted By: WillInAberdeenYes, that's where I was going last paragraph.... (nicely explained Simon!) . Running the ufh at that temperature (so giving ~20W/m2 output) would put ~1kW heat into a 50m2 classroom, which might be enough. Adding ~3kW of body heat would require the 1kW heating to quickly become 2kW of cooling, need to let the thermal mass absorb some of that.

    But observed on the school run today: the heating does need enough oomph to cope with several sets of double doors being propped open in mid December to let everyone out! Probably couldn't boost the UFH temp to get enough kWs out to respond to that quickly.


    Thanks. I just checked my heating system. 8C outside at the moment and the flow temperature is 22.5C.

    The other thing I've noticed after a few years of living in a very well insulated house is the way thermal mass regulates temperature. We've got a concrete floor and Fermacell walls (so almost twice the wall mass compared to plasterboard - a quick google suggests 14kg m2 vs 8kg).

    If we open the doors and flush though all the air on a cold day the house warms up again remarkably quickly. Whenever the subject of moving heat through the ventilation system comes up people point out that air just doesn't hold enough energy to do that effectively. If you've got a cool building structure and are relying on warm air you do need high output but with enough thermal mass you can get away with having the doors open for a while.

    Obviously needs proper calcs done, might not be cost effective. Occupation pattern is different for a home to a school - we've tried turning our heating to 'holiday mode' when we've been away in winter and it does take a few days to get back to comfort after a week or so switched off (though we don't have any internal thermostats - wouldn't be difficult to build some logic that compensated for a lower internal temp to boost flow).

    So basically - low temperature weather compensated variable flow temperature UFH works well in a well insulated house with some thermal mass. Whether its the best solution for a school I've no idea
    • CommentAuthorbarney
    • CommentTimeDec 17th 2019
     
    I worked on the design of a number of PFI schools as part of BSF.

    We spent a lot of time developing design solutions for ProjectCo and settled on what we called ultra low temperature UFH (we were operating at 27C flow and 22C return for a floor temperature of 20C.

    Heavy floor slab - well insulated below, dense internal masonry structure (helps with BB101 acoustic considerations) with significant external insulation behind a range of facades (cladding, brickwork etc)

    We paid a lot of attention to indoor air quality, good fenestration design (for good daylight but limited overheating), responsive lighting, local CO2 sensors and a mixed mode ventilation system (trickle and purge)

    They were very successful, have outperformed similar schools of the era, have proved simple and cost effective to operate for FMCo, have never triggered non availability penalties and made the man with the big cigar an awful lot of money.

    It can be done, the client needs to enable the design teams to make it happen - which is basically the key problem based on trading capital for revenue - PFI understood that - the client often doesn't and feels hamstrung by the available funding so accepts solutions based on CAPEX and not on the whole life cost which has to include OPEX.

    Regards

    Barney
    • CommentAuthorSimon Still
    • CommentTimeDec 17th 2019 edited
     
    Posted By: barneyultra low temperature UFH (we were operating at 27C flow and 22C return for a floor temperature of 20C.


    Of course - I was forgetting that the actual floor temperature would be different. Flow temperature *leaving* the boiler is 23.5C now but the actual floor temperature read with my cheap IR thermometer is below 21C. no idea how accurate those measurements are.
    • CommentAuthorCWatters
    • CommentTimeDec 19th 2019
     
    Does the contract require a specific "Display Energy Certificate" target?

    https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/452481/DEC_Guidance__rev_July_2015_.pdf

    "This guide describes the obligations that come into force for buildings occupied by a public authority where, from 9 July 2015, the total useful floor area of the building exceeds 250m^2 and which is frequently visited by the public"
    • CommentAuthorMike1
    • CommentTimeDec 21st 2019
     
    FWIW, my primary school was built in the 60's and had electric underfloor heating throughout. From a user-perspective it was great - I spent plenty of time sitting on it :)

    Unfortunately I was rather too young to enquire about energy efficiency or economic aspects (both probably poor - I doubt that it had much insulation), but clearly it can be done...
  6.  
    Posted By: WillInAberdeenKids are in school for 6 hours of each weekday in term, so less than 15% of the overall time. Teachers for 9 hours. Otherwise there's nobody there but the stick insects. Each room has sudden changes of occupancy, from zero to 30 kids at 9am Monday morning, and vv at lunchtime, so needs either lots of thermal mass or rapidly responsive heating.

    Barney's given the pro advice, just to add that our local council procures all the new school buildings from a panel of developers through a Scotland-wide programme. This involves lots of multi-project type specification documents that are used for 100+ schools. Typically they specify what temperature they want the different rooms to be and how much they want to pay for heating. The developers then make bids in which they propose how they will design and heat the building. If they can save money vs the spec, their bid gets extra score. Once the process is done and the project is awarded to a developer, it's very hard for the council to come back and say they want it heated or insulated differently. CoP, is there a similar process where you are, can you influence the project specs before bid?


    I'm trying to get to the bottom of what's happening. We're only parents, so we have little say. I think the county council has issued a specification document that the developer is working to (and nothing else). I'm trying to get hold of it.
    •  
      CommentAuthordjh
    • CommentTimeDec 22nd 2019
     
    Posted By: ComeOnPilgrimI'm trying to get hold of it.

    I'm no expert but I suspect there must have been a public tender, in which case the spec will be part of that [public] documentation. Failing that an FOI request should get hold of it, I think. Always assuming a quiet word with your county councillor doesn't.
  7.  
    Looks like the only formal requirement is zero carbon in use. Yet it seems that the developer aimed to build a passive house standard building with environmentally friendly materials. As such they appointed a specialist architect they could deliver this. Yet it seems, possibly for reasons of cost, they they are dropping all this and building something very bog standard. No idea how or why this has happened, or whether anything can be done about it. I'm going to write to the council (who are the client) to see if I can find out more details.
    •  
      CommentAuthordjh
    • CommentTimeDec 28th 2019
     
    Posted By: ComeOnPilgrimthe developer aimed to build a passive house standard building with environmentally friendly materials

    There's a field next to us where that was proposed too :) It's all gone quiet at the moment ... Our district councillor thinks we should establish a community land trust but I've no idea how he thinks we would acquire the land.
    • CommentAuthortony
    • CommentTimeDec 28th 2019 edited
     
    I think that all new schools should be built to a lower energy standard than Passive Haus and should not need ufh
  8.  
    Designing schools to use less energy is a very challenging task, one which doesn't lend itself well to throwing ever increasing amounts of insulation at it.

    I have worked in schools which have 300mm+ of mineral wool in the external walls, large amounts of UFH, high spec windows, trickle and boost MVHR systems etc and they have been horrible places to work with large amounts of remedial work stemming from the implementation of these technologies.

    Responsive lighting - hugely expensive to implement and I can see no real benefit despite the specifiers telling us how they would improve attainment etc. Lights are normally fully on or fully off, the intermediate settings do little apart from want the room users desire a little more light as they notice the lights aren't as bright as they "should be". One nearly set a school on fire sitting smouldering for hours. An ongoing issue is a still classroom or hall full of people and the lights decide to switch off.

    CO2 monitoring - every classroom has a CO2 sensor which goes through the roof after an hour of pupils sitting in a room especially on a wet day. High spec windows of course don't open to help with air changes as the designer has ordained that the MVHR system will compensate and boost the room air changes and users are too stupid to be allowed to decide when they can be opened. The MVHR system can't sort out the air issues in a timely manner, because the racket of moving that much air would be unacceptable, teachers also having time off work due to ongoing issues due to MVHR outlet positioning causing excess drafts and increased noise. Increasing the room volume by using higher ceilings helps, but it is more money.

    The most pleasant rooms by far are any computer rooms which have air conditioning complete with user controls. Don't underestimate the difficulties of moving large numbers of people into a room for what may be a relatively short period of time. It is a very different to designing a house, and even when you let specialists loose who produce wonderful plans with what looks to be great eco specs it might not work quite as expected.
   
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