General: In the long run high tech building solutions have no future

61 to 80 of 80

- CommentAuthorPaul in Montreal
- CommentTimeFeb 7th 2008
Posted By: Mark BrinkleySmoke detectors are a good example. They are simple and easily maintained, but you'd be surprised just how many aren't.

Over here, the fire brigade come by once a year to check the smoke detectors. Mechanical systems do break down - but all homes require maintenance so I'm not sure it's really a valid point. People have to take responsibility for themselves - there's no two ways about it unfortunately.

Paul in Montreal.
- CommentAuthorBowman
- CommentTimeFeb 7th 2008
I think Chris raises a very important point and an issue that underlies the image of sustainable/environmental/green ideas in general, most people see green issues as needing large sacrifices; a big dent on their free time, a big dent on their wallets, and a big dent on their quality of life in general. For the suburban majority green just isn't an issue, green is for hippies. I think this is probably the biggest issue facing sustainable causes, how to ensure that the future really does offer a higher quality of life, and more importantly that this is also the general perception.

(Blimey I think someone must've put something in my tea...)
- CommentAuthorPeter Clark
- CommentTimeFeb 7th 2008
Posted By: Paul in Montrealfully passive systems are almost never adequate

Citation?
- CommentAuthorPaul in Montreal
- CommentTimeFeb 7th 2008 edited
See pages 26 and 27 of this interesting presentation based on decades of research in Canada

http://www.buildingscienceconsulting.com/ventilation/2006/Reardon.pdf

I'll leave it as an exercise for the reader to do the requisite googling to bring up the related research that's summarized there.

[edit: here's a paper summarizing all types of ventilation systems with a rich set of references: http://www.buildingscienceconsulting.com/resources/mechanical/ventilation/Residential_Ventilation_Technologies.pdf
and a delightful quote: "there is no hole for all seasons" ]

Paul in Montreal.
- CommentAuthorPeter Clark
- CommentTimeFeb 7th 2008 edited
Hi Paul,
Thanks, both are very interesting especially the second, which however, will not allow me to cut and paste material to discuss.
It seems that research in Canada and America shows passive ventilation is not as good as powered in maintaining reliable air quality all the time. But research in the UK and EU shows that a particular way of doing it, passive stacks and air supply windows, IS GOOD ENOUGH most of the time.

Does this justify your remark ?

'fully passive systems are almost never adequate'

I am not sure, but I feel it is potentially misleading for people in Europe.

I am very interested in this, from page 19 of your second ref. (typed by your willing servant)

Yoshino et. al. (2003) has shown that a hybrid system can provide adequate ventilation rates even when weather conditions created poor ventilation in the passive system. By using a fan to boost stack ventilation during times of low wind speed under ventilation was prevented. And by using a damper control at the vents, over ventilation was prevented when temperature differences were large.

The Dwell-Vent system uses such a damper, but not currently a fan. Perhaps we are not so far apart in this after all?

Peter
- CommentAuthortony
- CommentTimeFeb 7th 2008
There is quite a big difference in energy saving terms! Passive stack throws away 100% of the heat in the ventilated away air.

MHRV on the other hand only wastes 10 - 15 % of this precious heat in the ventilated away air, further it can also capture some latent heat from the moisture in it.

Add this to the inadequate rates of ventilation in some circumstances and we a non starter in the race

The benefit of whole house systems is that all rooms get air changes all the time and this is not necessarily the case with passive systems.
- CommentAuthorPaul in Montreal
- CommentTimeFeb 7th 2008 edited
There is active research (pardon the pun) in Canada of combining passive and mechanical systems to further reduce energy usage. There are many times of year where passive systems are adequate - so it doesn't make sense to run fans (and consume energy) at these times which also coincide with a minimum level of heat recovery. At other times of year, mechanical ventilation is required - both to facilitate heat recovery and provide adequate ventilation. So we're not far apart at all! The main problem with passive-only ventilation is that it is hard to control and is therefore subject to the vagaries of the driving forces, especially in urban areas (as discussed in the papers). A hybrid approach is probably the best compromise in a moderate climate like the UK - and even here in Canada in many locations.

The problem with using windows (in winter) as a supply of air is the negative psychometric effects. Even though the incoming air may be somewhat warmed by the window, it is still cooler than the ambient air in the room and the feeling of a cool draft may induce the occupants to raise the thermostat to compensate for feeling cold, even though the ambient air temperature may be at a comfortable level. This harks back to the discussion on radiator placement versus energy usage - sometimes the optimum placement from a heat loss perspective leads to a feeling of discomfort, raising of the thermostat and an overall higher consumption of energy than would have been the case.

Anyway, hopefully the material in the papers will stimulate further discussion as the references are pretty comprehensive. What I found interesting is that average airtightness figures in Canada 20 years ago were ahead of what is proscribed in Part L now. And those figures are way worse than current practice over here.

Paul in Montreal.
- CommentAuthorPeter Clark
- CommentTimeFeb 7th 2008
Posted By: tonyThere is quite a big difference in energy saving terms! Passive stack throws away 100% of the heat in the ventilated away air.

But passive stack AND air supply windows do not throw away all the heat, some is recovered in the window by two processes

- heat that would otherwise be lost through the window is picked up by the incoming air

-Solar may contribute to warming the incoming air

Posted By: Paul in Montreal though the incoming air may be somewhat warmed by the window, it is still cooler than the ambient air in the room and the feeling of a cool draft may induce the occupants to raise the thermostat to compensate forfeelingcold, even though the ambient air temperature may be at a comfortable level

Paul, it seems to me that 'may' is the operative word here, this is a question in need of empirical evidence, precisely the kind of evidence Dwell-Vent spent several years gathering in the UK, Poland and Ireland. In the reports of occupant satisfaction that I saw, no one complained of cold draughts that I recall, and fuel bills were down substantially compared to the control houses.
It is a matter of how this works in practice, that clearly involves the local climate, the building, and the occupants' feelings.
- CommentAuthorPaul in Montreal
- CommentTimeFeb 7th 2008
Posted By: Peter ClarkBut passive stack AND air supply windows do not throw away all the heat, some is recovered in the window by two processes
- heat that would otherwise be lost through the window is picked up by the incoming air
-Solar may contribute to warming the incoming air

Hard to see how solar would do this at night - when the incoming air is coldest. Plus all of the latent heat of the exhaust air is lost.

Posted By: Peter Clarkfuel bills were down substantially compared to the control houses.

Wonder if they were really comparing apples to apples. Did the control houses have the same level of air tightness? If not, then it's not a valid comparison - though compared to leaving windows open I suppose this may account for the difference. But that's not a parameter of building performance, that's occupant behaviour. I'm sure occupants would be more satisfied by supply air windows than trickle vents / open windows, but that may by as much due to ignorance (of what high quality low energy MHRV is really like) as much as anything else.

In a damp climate like the UK, IAQ (interior air quality) is difficult to control if air tightness improves to the sort of levels we have over here in Canada and may lead to the sort of problems encountered in Vancouver (very similar climate to much of the UK). Mold and rot became serious issues because air tightness had been improved but mechanical ventilation wasn't used (there were some other issues too with damp ingress). There were serious health issues at the time due to allergies to the mold spores. Had properly designed ventilation systems been mandated at the time, these issues could have been avoided. But that, of course, is hindsight. Since the UK seems to be about 20 years behind the current state of the art, these prior lessons learned are important to avoid creating the same health issues. I'm sure passive systems can work in some circumstances, but it's hard to design them correctly to guarantee this. Mechanical systems are easier to design since there is control of most parameters of operation, which means that certain minima can be achieved - such as ensuring correct ventilation rates in all rooms - something that's very difficult to do with passive systems. It surprises me how much resistance there seems to be to these systems - they're a very tiny percentage of the overall cost of a building, cost very little to run (since they save so much energy in the first place) and are virtually silent if designed and installed properly (which is not difficult).

Paul in Montreal.
- CommentAuthorPaulT
- CommentTimeFeb 7th 2008
Paul in M - I daily have to explain the benefits of HRV. The really scary part of all this that we have the highest allergic asthma levels in Europe and I am still fighting for budget to be moved away from the kitchen!

Also we use a new type of plastic electrostatic filter with ultra low air resistance; No other system in the UK has it so I will not say who we get it from, but we had to import it from your continent. (this is regarding salt corrosion).

20 years behind - and the gap is widening, for example France had mandatory Whole House Ventilation in 1986 (not saying they do it, just that it was manadatory from that time)

Supply air windows. To work they MUST be reducing the surface temperature of the inner glass leaf (heat energy has to come from somewhere. This will create a lower surface temperature and hence degrade thermal comfort. One of the reasons why PAssivHaus specify triple glazing is the improvement in thermal comfort due to higher surface temperatures. In addition the exhaust air is still dumping the conditioned air 12 times per day (assuming ventilation targets met). So if all of this heat is leaving the building how can heat recovery take place in the windows?

--- The more I think about it the more it does not add up.

BRE tests - they will take the money and do the research without caring about the results (as good Scientist should always do)

Also the negative pressure in the home must also be pulling in more air through infiltration, not a good thing to happen at all; On this basis the need for ultra air tight home is more accute in such homes.

Also how are you supposed to deal with bungalows where the the driving forces are low (no significant passive stack and low to the ground, hence sheltered).

If passive stack is used to drive the system (I assume this because if you have a mechanical whole house ventilation system you might as well have a full HRV) how does a top floor bedroom window ventilate if it is a zone of negative air pressue on the lee side of the house.

- I know absolutely that homes will experience different pressures in different zones according to climatic conditions (we perform air tightness test and have to measure the pressure accross the building within certain tolerances).

It is clear that Supply air windows share many factors with trickle vents and they (ttrickle vents) clearly do not work.
---------
Note on thermal comfort: A 1C drop in overall surface temperatures is equivalent to a 1C drop in air temperatures (typical conditions in the home, clothed and sedentary occupants)

Remember that we should be designing the achieve thermal comfort, not an absolute air temperature. this is particularly the case with the elderly who have quite distinct requirements - not even considered in ASHREA and BS/CIBSE (etc) guidance. When one of my colleagues challenged this (with CIBSE) she was told that the elderly can always put more clothes on! (Not true by the way as they do not know when they are cold, sorry about the 'they' will be me one day).

Fire checks - we used to have inspections by the Fire Brigade in England but was cut so they all seen to be filling in their time decorating now!
- CommentAuthorTuna
- CommentTimeFeb 8th 2008
Posted By: PaulTSupply air windows. To work they MUST be reducing the surface temperature of the inner glass leaf (heat energy has to come from somewhere. This will create a lower surface temperature and hence degrade thermal comfort. One of the reasons why PAssivHaus specify triple glazing is the improvement in thermal comfort due to higher surface temperatures. In addition the exhaust air is still dumping the conditioned air 12 times per day (assuming ventilation targets met). So if all of this heat is leaving the building how can heat recovery take place in the windows?

--- The more I think about it the more it does not add up.

Paul, as I understand it, the cooler middle leaf glass doesn't have to mean dramatically reduced temperatures on the inside glass surface - instead of a heat gradient across two panes of glass, you have it across three. The air across the middle leaf isn't any colder than normal outside air (though it will be moving at a constant rate), so the window isn't being asked to do much more than it would if it were just a normal double glazed window.

In comparison to normal double glazing (where cold air from trickle vents isn't normally much of a source of complaints), the air from a supply air window is closer to the inside temperature, so the comfort levels should be good. HRV will reduce the difference to zero, but there is a law of diminishing returns here - zero sounds good, but if you don't notice (or even enjoy) a slightly lower temperature source of fresh air in a room, there's no practical benefit. I've read a few discussions in here on whether triple glazing has any benefit over double in the UK climate and a similar conclusion seems to be reached - that you can save more energy, but it's not worth the efforts to do so.

You ask how the heat leaving the building can stack up with heat recovery. Again, as I understand it, the point is that a relatively large percentage of fabric losses of a house are through the glazing. Air supply windows reduce the heat loss through glazing (lower effective U values), so venting warm air is offset by much lower fabric losses.

Without more studies, it's hard to judge. My impression is that there is a scale of energy efficiency between normal double glazing on a traditional build and full airtight build with MHRV. Passive stack and air supply windows sit somewhere between the two. The advantage over MRV may be a quieter, maintenance free system with lower embodied energy. Whether the (possibly) higher efficiencies of HRV offset that is another question. In some ways I wonder if the current obsessions with Passiv Haus might be sidelining other building methods that would offer similar levels of energy efficiency with other benefits.
- CommentAuthorPeter Clark
- CommentTimeFeb 8th 2008
Posted By: Paul in MontrealWonder if they were really comparing apples to apples. Did the control houses have the same level of air tightness? If not, then it's not a valid comparison

Oh good point Paul, maybe the people at Cambridge University and BRE who designed this study don't know about designing a fair test. I'll get in touch right away, I'm sure they will want to rethink the whole project!
- CommentAuthortony
- CommentTimeFeb 8th 2008
Ah, so passive systems are not for PassivHaus or better insulated buildings then?
- CommentAuthorTuna
- CommentTimeFeb 8th 2008
Posted By: tonyAh, so passive systems are not for PassivHaus or better insulated buildings then?

Sorry, who suggested that?
- CommentAuthorPeter Clark
- CommentTimeFeb 8th 2008
On this page entitled 'What is a passive house?'

http://www.passiv.de/English/PassiveH.HTM

it says at the top
'A passive house is a building in which a comfortable interior climate can be maintained without active heating and cooling systems (Adamson 1987 and Feist 1988). The house heats and cools itself, hence "passive".'

Further down we find
'Highly efficient heat recovery from exhaust air
using an air-to-air heat exchanger:'

And of course this is accomplished by having a 'non passive' fan. Also generally people will use a 'non passive' electric resistance heater in the ventilation system.

We could conclude that this impressive and extensive initiative has failed to create a passive house without these electric 'non passive' elements, and therefore that is that - we need fans and electric heaters in well sealed houses.

Alternatively we could say that this impressive and extensive initiative has failed to create a passive house without these electric 'non passive' elements, and so what other ideas and initiatives are there about how to make a truly passive house.
- CommentAuthortony
- CommentTimeFeb 8th 2008
Could we power the necessary fans from pv solar panels with battery backups? and call it Passivhaus still?
- CommentAuthorPaul in Montreal
- CommentTimeFeb 8th 2008
Posted By: tonyCould we power the necessary fans from pv solar panels with battery backups? and call it Passivhaus still?

Yes, that would work. What probably wouldn't work would be using PV to power the auxiliary electric heating that some passivhaus MHRV systems have. However, using solar thermal with hot water storage would solve that problem.

A different approach to achieving a passivhaus was taken at a development in Montreal which is zero energy when averaged over a year. It has PV, solar thermal and ground source heat pumps (as well, of course, as HRV). Over a year, there is net zero energy usage as the excess electricity produced over the summer is "stored" in the hydroelectric systems here (by effectively using less water) and is then "borrowed" in winter to run the GSHP - but the net consumption is zero or less. See http://www.ecocite.ca/home.html

And even passivhouses require things like lights, refrigerators, computers etc. :)

Paul in Montreal.
- CommentAuthorChris Wardle
- CommentTimeFeb 8th 2008
What's happened to Ethics-Man? He's set us all off and then done one!
- CommentAuthorPaul in Montreal
- CommentTimeFeb 8th 2008
Posted By: Chris WardleWhat's happened to Ethics-Man? He's set us all off and then done one!

Not very ethical, that!

Paul.
- CommentAuthorChris Wardle
- CommentTimeFeb 16th 2008
Has anyone thought about the possibility of combining supply air windows with an exhaust air heat pump to heat the domestic hot water?

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