Passive cooling

[Nick Grant]

This current warm spell is a good chance to see how passive building are performing without aircon. Is everyone ringing clients to see what the temperatures are????

I have to fight with my partner to keep the doors shut in the heat of the day but she keep opening them. Hence temp has topped 25C but still feels cool.

Interestingly our light weight timber hut that we lived in for 7 years has been shut up and when I went in the other day it felt quite cool. Suggests to me that insulation is more critical than mass? Not what I'd have expected intuitively.

[Anonymous]

I have to fight with my partner to keep the doors shut in the heat of the day but she keep opening them. Hence temp has topped 25C but still feels cool.

Must be hard to not want to open doors/windows in weather like this, how much impact would doing so have? i.e. what would the temp be with the doors shut?

[SimmondsMills]

nick
I suppose insulation may be more critical than mass if the building has no doors – or no occupants 🙂

Tahir, I think (but may be wrong) that Nick means that by opening the doors the building is heated up by hot outside air entering, and if his partner listened to his good sense then the building would hold onto its coolth. Nick – does your long suffering partner just leave the doors open 'en passant' or is it to achieve a nice draught?

[Anonymous]

Tahir, I think (but may be wrong) that Nick means that by opening the doors the building is heated up by hot outside air entering, and if his partner listened to his good sense then the building would hold onto its coolth.

I know, what I meant was how much affect on internal temparature would leaving the doors open have, we're very prone to leaving the back door open in all kinds of weather (summer and winter) and especially when it's hot out it's counter intuitive to actually start closing windows and doors to keep the house cool.

[Nick Grant]

Andy

To let the sun rays flow in!

Tahir

We tend to have doors and windows open quite a bit but heat gain in summer when it is 30C outside and heat loss in winter when it is cold are obviously significant although thermal mass does slightly hide the effect by taking a while to heat up or cool down but heat loss or gain is a function of the airflow and temperature and thermal mass doesnt reduce the actual energy loss.

Hope that makes sense!

Obviously you can have the heating or aircon on and windows wide open if the boiler is powerful enough 🙂

[SimmondsMills]

tahir
talking to an australian teacher she said that they were brought up to leave the windows open at night and close them during the day – if they left them open in the heat of the day they would be told off. This explained why she was overheating in the building we were conversing in – in Oxfordshire. The staff had forgotten that they could leave all the trickle vents open at night in periods of hot weather to cool the building for the next day, consequently after 2 days of very hot weather the offices (and one of the classrooms) were getting to 29 degrees. They will try the trickle vents at night now..opening the windows or rooflights is a no no as they are either worried about security or moths getting in and setting off the alarm system! Thermal mass in this building is concrete floor and 50mm of clay plastered Heraklith board (walls) throughout most spaces, with one rammed earth wall in the lobby.

[Anonymous]

Design, implementation and usage, so shouldn't she have some kind of induction into how the system worked?

[Julia Bennett]

Andy

The construction of the building in Oxfordshire sounds lovely – 'thermal delight' as Sue Roaf would say – even if the users forget sometimes how to use it. Have they got the hang of the trickle vents now? Have they noticed the difference.

In a previous job, we used an automated night purge system for a new school building in Banbury to overcome security and moth issues. Not technically passive but low power…

Sadly I hear no data is being collected on its performance, so it may be time for me to go back and ask the staff how they got on last term. I have tried to track down funding for post-occupancy study of this and several other (more passivley cooled) schools, but to no avail, though 'usablebuildings.com' network was very helpful and responsive (thanks Adrian et al).

Perhaps the Energy Performance of Buildings Directive will have an impact on this area….

Julia

[David Olivier]

I can report that

1. the stone cottage I'm renting while I build my own got to the dizzy heights of 23 deg C.
2. an energy-efficient house built 20 years ago in London got to 22.5 deg C.

London gets much hotter than the Marches, so the 2nd example is much more impressive than the 1st. It's merely an infill mid-terrace house with due N-S orientation, very good insulation and the construction is more German than British – masonry external walls, masonry internal partitions, concrete upper floors and stairs, topped by a timber roof. It's occupied by a family of four – the husband is an architect – and I was told during the 2003 heatwave that the only dwellings in the entire area fit for habitation were this house and a house which has had air conditioning retrofitted.

The 10 year old Elizabeth Fry Building at UEA continues to stay <22 deg C in the basement zone, which has automated night cooling and CO2 controls on the ventilation. It's mostly made up of 100 m2 lecture theatres occupied at peak by 100 students. The top three floors of the EFB have less automation and here staff tend to open the windows in heatwaves – which raises the air temperature inside the offices, although it may give them a cooling breeze.

I think air conditioning in the UK climate is an artifact of incompetent architecture, but of course it continues to spread and uses energy which makes climate change worse.

[SimmondsMills]

Julia / Tahir,

We did prepare a very fulsome building manual, with A3 summary pages on operation / maintenance for fixing to the office walls. All was fine for the previous summer, with trickle vents and windows used correctly, but staff changes led to the building manual not being used. In addition to not using the`trickle vents at night,  the teachers did not open high level windows during the day in this period (no doubt being very busy and distracted), and with 35 school kids in a sunny well insulated classroom – it got hot!

We have two years monitoring results now (water, electric and wood fuel), and we know the building actually meets its initial design claims wrt CO2 emissions – through high levels of insulation, reasonable airtightness, pretty good detailing to reduce thermal bridging (based on' I' beams / studs/rafters + external insulation board to roof), good passive solar gain and excellent daylighting. A significant reduction in CO2 was achieved with all of these factors allowing the building to be heated with two domestic scale  wood stoves burning local wood – logs from the nature reserves. I am on a laptop, not at my desk, but will put up later here the monitored CO2 emissions for this building. I wanted to see what the CO2 emissions would be if it was heated with gas, rather than wood…but we have to save up to pay an energy consultant to answer this question…soon.

I think the overheating problem is not significant, but the management of ventilation and cooling of this building is not 'fit and forget', but is pretty basic and simple in operation. Designing to AECB Silver and Gold standards (which is our office's aim now) may lead us to less 'hands on' solutions….

Julia, could you give me a little summary of how the automated night purge system works in your Banbury school..fans pulling air through floor ducts in concrete (ground/first) floors, computer controlled / simple timer?

As to getting funding to learn from what works and what does not, post occupancy…what can I say…. :'(

[David Olivier]

Julia

Could I repeat Andy's question about your night purge system and ask: is it linked to the building mechanical vent. system … or does the building have no other mech. vent. system? (some don't).

David.

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