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Maximum home comfort and the Great British Insulation Scheme fiasco.

John Greengrass
This has nothing to do with NET ZERO.
It is to provide: -
  1. Vastly reduced energy consumption in the UK, fewer new power stations.
  2. Maximum home comfort, no more cold or hot or damp homes.
  3. Due to 2, a large reduction in visits to hospital reducing costs to the NHS.
When insulating the exterior face of the building you are trying to obtain STS (structural thermal storage), i.e. getting then walls and contents to remain at a sleeping temperature summer and winter so that the structure is the radiators.
It is obvious to any building services engineer that the Great British Insulation Scheme will cause mould as insulating a building seals the building.  
When we live in a building we produce water from breathing, sweating, bathing, cooking etc. and if it is sealed then the water can’t escape and mould grows, an adequate mechanical means of water extraction must be installed. Heat recovery extract fans and heaters must be installed in bath / shower rooms and kitchens and reversible air-to-air heat pumps (RAAHPs) installed elsewhere. 
The reversible air-to-air heat pumps (RAAHPs) are not those with radiators as they inefficient as radiators need 80°C and heat pumps can’t get anywhere near that temperature and they do NOT take out water.  RAAHPs can provide hot air at 30°C or cold air at 16°C or any temperature in between, whatever the temperature is outdoors, at the turn of a switch and they remove water at the same time. They are the cheapest way to provide heating and can be installed in any property. They must be installed by Fgas registered engineers. They have an outside unit, floor standing or fixed high on an external wall and small fan units high on the wall in the room where they are needed, they are very quiet and cost as little over £1000 per room. The pipework can be installed within the structural thermal storage external insulation, so the installation can involve little disruption.
The only maintenance required is to clean the filters regularly which anybody can do with a vacuum cleaner. If there is a problem the RAAHP just stops working.
They don’t provide hot water so the boiler would need to remain, or an electric boiler can be fitted, if there is a immersion heater that will do the job.
I have had this system fitted for 10 years with no problems and very small heating bills.
The Great British Insulation Scheme is a grant for the screwing roofing battens every 60cm onto the existing pebbledash/render of concrete or brick (solid or cavity) walled homes and over that 7cm insulation board and then sealing the building with coloured silicone render. The insulation of RAAHPs must be a requirement to enter the Great British Insulation Scheme otherwise it is a grant for damp homes.
John Greengrass
  • John Greengrass said:
    It is obvious to any building services engineer that the Great British Insulation Scheme will cause mould as insulating a building seals the building.  

    That's not an obvious consequence at all. That's because it confuses ventilation with insulation.

    I would agree that many in the insulation industry and trades are unaware of the confusion and can fire off stupid ideas about how great their little bit is without realising the other aspects that are needed for a more optimal system.

    And that's all before the ignorances (not knowings) of the great British pubic and media.

    Having had to replace the rotten floor in a ground floor room, resolve gutter, down pipe and drain issues, have a roof replacement (rotted sarking on North aspect), cavity wall insulation, solum covering ('seal'), added window vents, created my own dampness chart to help inform, etc., I feel slightly able to comment...

    One of the big problems is that historically, we heated the person (Tea & woolly jumpers), and the room (fire place, curtains & pelmets, closed doors & sausage dog draft excluders), condensation and jack frost on the winter windows.

    We (the public) have totally flipped to expecting shirt-sleeved open plan living, with background heating, but still keep doing all the old household habits based on high air flow leaky housing (e.g. clothes drying on radiators and banister rails, sealed double glazing, etc).

    A recipe for disaster (as you highlight!).

    Insulation isn't the problem. Understanding the trade-offs and learning the appropriate life-style is. There are some great lectures from Dr J Lstiburek that cover some of those trade-offs (and UK's oceanic climate is a difficult environment)

    (the Dampness chart is in previous discussion  RE: Structural thermal storage )

  • I think you've got the right general idea there - but I'd take issue with a lot of your details, and there are many more options than you seem to suggest.

    As I understand it RAAHPs will only remove moisture from the room when they're in cooling mode (when the coils are cooler than the dew point so condensation is formed) - so most of the year they will be ineffective as a means of controlling damp. Radiators can certainly work effectively way below 80 degrees - we've been designing for system temperatures below 60 degrees since the introduction of condensing gas boilers decades ago - increasing the sizes of radiators again to better fit heat pump characteristics is certainly possible (and is done). Another option is wet underfloor heating - certainly for new build and major referb projects - the "warm toes" effect often allows slightly reduced room temperatures while preserving comfort and the lack of noise and even heating is often appreciated by consumers. Wet heat pumps can easily produce 55 degrees plus (some can go as high as 75 degrees) so can usefully heat domestic hot (tap) water too - and significantly more efficiently than an immersion heater or electric boiler.

    As for moisture control, my preference is whole house heat recovery mechanical ventilation. Unlike single room units it naturally draws air right across rooms rather than trying to ventilate a whole room from a single point, and can use excess heat from bathrooms and kitchens to pre-heat the rest of the house. Again more easily fitted in a new build or major refurb situation, but an option all the same.

       - Andy.

  • in reply to AJJewsbury

    insulating a building seals the building

    Thinking more about this, while it should, I suspect often it doesn't. Ventilation to suspended timber ground floors needs to be maintained, which in many older properties means the wall cavity is also ventilated (as air bricks traditionally weren't sleeved as they pass through the outer walls), then inevitable gaps around joists where they are supported by the inner leaf of outside walls (or gaps around pipes or just missing bricks) means the air flow can continue into floor voids, and often into the loft space as often the top of the cavity wasn't closed either. I've even found draughts coming up the underside of staircases - as there was a gap between timber staircase itself and the lath & plaster angled ceiling below it - which effectively joined the underfloor area to the landing floor void. Insulation can be tricky to do properly.

       - Andy. 

  • in reply to AJJewsbury

    Answering Andy

    RAAHPs re mainly for heating and at press of a button can cool or just dry. Heat pumps most efficient temperature is 30C no good for radiators

    In my blog I am talking about external insulation and double glazing sealing the building which prevents enough ventilation to allow for the damp from breathing, sweating, bathing, cooking etc. being expelled from the building which is what happens under the Great British Insulation Scheme and how to overcome it. The ventilation and draughts you mention are another discussion that I hope others take up.

    John

  • in reply to John Greengrass

    I am talking about external insulation and double glazing sealing the building which prevents enough ventilation to allow for the damp from breathing, sweating, bathing, cooking etc. being expelled from the building

    That shouldn't happen though - building regs (part F) generally demand suitable ventilation see https://assets.publishing.service.gov.uk/media/61deba42d3bf7f054fcc243d/ADF1.pdf and the Domestic Ventilation Compliance Guide) - and that would apply (at least to the extent of not making things worse) to changes to existing buildings as well as new builds (e.g. when fitting new windows). If there's not better solution the the minimum would normally be trickle vents in the windows - so not really sealed at all. (Of course regs aren't always complied with, but that's a different issue).

    Moisture isn't the only problem ventilation solves either - presuming you have living breathing occupants then there's oxygen to replace and CO2 and all sort of indoor pollutants (from odours to spores) to expel. I'm not sure RAAHP would achieve all that, even if it switched modes automatically.


    Heat pumps most efficient temperature is 30C no good for radiators

    HP efficiency is certainly best at lower flow temperatures, but that doesn't completely rule out radiators with heat pumps. Larger radiators can still provide sufficient heat to a room even at reduced flow temperatures (say 45 degrees ballpark) - even better when the place is properly thermally insulated as heat demand will be lower than before. Many wet heat pumps have optimising controls that allow them to vary flow temperatures depending on the difference between indoor and outdoor temperatures - so when it's less cold outside, and so the rooms need less heat to keep the temperature up, the HP reduces the flow temperature and benefits from improved COP. In the depths of winter the efficiency drops but the costs are still manageable over the year. There are certainly radiator based heat pump systems being installed and they do work. In many cases other options may well be more efficient, but they're still an option.

    Don't get me wrong, RAAHPs certainly have their place, and their USP of being able to provide cooling as well will certainly appeal to many at the moment (even if other methods, e.g. external shading to windows might be a better solution or at least contribution). I suppose I'm cautioning against over-egging their advantages or disregarding valid alternatives - such tactics soon gets seen through and then the valid parts of your message risk being disregarded too.

       - Andy.

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