Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)

Categories



Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

Buy individually or both books together. Delivery is free!


powered by Surfing Waves




Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.




    • CommentAuthordickster
    • CommentTimeNov 6th 2020
     
    Yeah, we tried it for a few days, but could hear it even on very low setting, couldn't be doin' with it., given that we are in quiet area. However, eyesight and hearing deteriorating now, so maybe give it a try again when deaf, but still able to watch large TV.:bigsmile:
    • CommentAuthorSimonD
    • CommentTimeNov 7th 2020 edited
     
    Mike 1
    So far as I'm aware, that has only been reported in older / lower spec timber frame buildings - for example those that rely on an external building paper wind barrier for airtightness. I don't recall reading any reports of significant variation when a fully taped dedicated vapour barrier has been correctly installed.


    I’ll link to a study made in Sweden from 2015 that looks at 3 buildings, 2 of which are timber frame, one of which is concrete form. All pretty well detailed. The timber frame buildings in the study showed that airtightness does vary across the year, correlating with RH – the higher the RH the tighter the building. The concrete building just saw an increase over time.
    Of course, this could have to do with poor onsite detailing, but it is also surmised in the study that movement of the frame due to RH variation across the year may lead to crimping and such of the airtight layer – thus leakage potentially caused over time.
    The suggestion made in the report is that airtightness testing should be conducted several times following initial construction.
    Here’s the link to the study and unless you read Swedish, you may need google translate:
    https://www.chalmers.se/en/projects/Pages/LufttQthetens-variation-Qver-Qret.aspx


    djh wrote:
    It'd be nice if you provided links to these studies you mention so other people can refer to them.


    Indeed, the particular one I mentioned I can’t find but IIRC it was either a German or Dutch paper. However the PHD thesis I’ve linked to below mentions some similar behaviour with occupiers ignoring the passivehaus manual and leaving their bedroom windows open at night in the winter.


    djh
    I'm not sure it would make much difference. Yes, sure, the humidity in a hygroscopic house will behave differently to the humidity in a 'plastic' house but hygroscopicity doesn't affect other pollutants.

    SimonD
    I understand that, my point was more to do with how human perception of and relationship with the environment will affect behaviour, consciously or unconsciously, and thus impact on overall energy consumption of the house.

    djh
    I'm not sure I understand that, so again a link to some explanatory material would help.


    This was more a propositional statement but I’ll quote from a PHD thesis I read (link below) that deals with some of this:

    “The importance of occupants’ everyday practices was highlighted by the literature on ‘practices and behaviours and domestic energy consumption’(Hargreaves et al., 2013; Firth et al., 2008; Owens & Driffill, 2008). Research exploring occupants’ practices and the possible effects on energy consumption show that there is a significant gap between the predicted and the actual energy performance of buildings, since occupants’ practices can vary to a great extent (Fabi et al., 2012; Socolow, 1978). Evidence shows that intended energy reduction outcomes in buildings may not be achieved as initially planned and in some cases any attained energy savings are short lived (Van Dam et al., 2010). This performance gap in energy consumption suggests that any possible benefit from the use of domestic technology solutions may be significantly reduced, or even invalidated as a consequence of occupants’ practices (Pilkington et al., 2011).”

    Link: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.761567

    My particular interest is how not necessarily how occupants’ everyday practices affect energy consumption of a building as I think given the research, that is a given, but rather how our relationship with both the building and immediate natural environment affect those practices, some of which we may not be aware of.

    And for me, the approach to simply provide a technical solution is inadequate. The same PHD suggests something similar:

    “.. research on MVHR has already demonstrated that these systems are failing to perform as initially intended (Balvers et al., 2012). Other studies show that the ability of these systems to provide adequate indoor air quality depends on many factors such as the existence of user friendly controls (Stevenson et al. 2013) maintenance of the system (Lowe & Johnston, 1997), performance (Kurnitski et al. 2007) and operation (Park & Kim, 2012; Balvers et al., 2008; Stevenson & Rijal, 2008). Many of these factors place the MVHR user as a key determinant of the effectiveness of the system, contradicting some assumptions that domestic technologies will produce the expected results if they are installed and functioning well (Shove & Guy, 2000).

    To link this back to my original discussion about ventilation, this same PHD cites a German study of ventilation (which I don’t have access to) where it mentions:

    “a study comparing the performance of ventilation systems in energy-efficient homes in 38
    Germany (Maier et al., 2009) identified a strong relationship between indoor CO2 concentrations and window opening behaviours.”


    SimonD
    Now, I'm referring to a tendency to design & build houses in the same way regardless of the environment within which they are going to be placed and how they're likely to be used

    djh
    It depends what you're talking about. Obviously designers tend to use techniques and materials that builders and regulators are familiar with, and reuse parts of designs where they can to a greater extent than I and many others would prefer (as a matter of cost-reduction). But all the planning applications I've seen recently of any scale have talked about orientation with regard to solar input and street design and so forth. Some are better designed than others but that is inevitable.


    Okay, let’s link that to my propositions about behaviour and relationship with our environment. If CO2 concentrations are related to window opening behaviours (it is clearly a pre or non-conscious sensory behaviour because of CO2s characteristics) , then utilising building techniques that naturally reduce indoor CO2 levels, may then have a significant effect, over the life-time of the building, on its overall energy use (and many other things).

    I’ll quote from another study on this particular point:

    “Simonson et al. (2004a) found that a permeable, hygroscopic building envelope primarily made of wood can affect the concentration of CO2, SF6 and water vapour. Such a building envelope can reduce significantly the CO2 concentration in low ventilation conditions, and still moderately when mechanical ventilation is provided. This building envelope reduced significantly the moisture fluctuations in a room in both well-ventilated and poorly ventilated conditions.

    Simulations of hygroscopic building materials also showed that they are effective in reducing peak humidity levels and to increase the minimum humidity level in winter. [11]. This study concluded that additional research was needed to determine appropriate hygroscopic and permeable materials for different climates and buildings.”

    https://core.ac.uk/reader/80323150

    Sensibly this paper suggests adapting to climate and buildings not assuming all materials will work equally well in all climates, even microclimates, I suspect.

    So this also suggests to me that the typical approach to MVHR installations regardless of the building fabric overlooks the nature of the building itself.

    For example, this Canadian paper, mentions how hygroscopic materials have an effect on HVAC systems leading to systems being oversized. https://web.ornl.gov/sci/buildings/conf-archive/2004%20B9%20papers/002_Simonson.pdf (this paper also covers differences between geographical location and thus climate)
    Overall, I’d hazard a guess that whilst builders, developer and governments like to use what they’re familiar with change of habitat is a human - social and cultural - issue, rather than a technical one.


    SimonD
    airtightness in a timber frame building is likely to vary across the seasons, with airtightness reducing during the winter months

    djh
    I don't see why that would be the case, given that the timber frame doesn't contribute to the airtightness?

    If you have the time and inclination, the study I linked to above looks at this.


    djh
    This all depends on the building techniques that are used and again its clear there are preferences to use techniques and materials that require less effort and thus cost, because cost is important and so is reliability.


    I’m not so sure I agree with the implicit assumption I read into here. I don’t think it has to require more effort and cost to adapt building techniques and materials. In many instances, it could yield a reduction – I’ve found the construction industry to be one of the most inefficient and wasteful industries I’ve come across in my life.

    I don’t mean all of this to become some evangelical rant, more that when it comes to ventilation, we’ve got a lot more to understand in terms of how it sits with the whole house design and those living within it, the energy actually consumed, health and comfort.
    • CommentAuthorMike1
    • CommentTimeNov 7th 2020 edited
     
    Posted By: SimonD
    Posted By: Mike 1
    So far as I'm aware, that has only been reported in older / lower spec timber frame buildings - for example those that rely on an external building paper wind barrier for airtightness. I don't recall reading any reports of significant variation when a fully taped dedicated vapour barrier has been correctly installed.
    Here’s the link to the study and unless you read Swedish, you may need google translate:
    https://www.chalmers.se/en/projects/Pages/LufttQthetens-variation-Qver-Qret.aspx
    Thanks :) I found the study (in Swedish) at https://www.researchgate.net/publication/44065408_Seasonal_variation_in_air_tightness_of_two_detached_houses and have summarised some of the key bits from Google Translate in the following separate post.
    • CommentAuthorMike1
    • CommentTimeNov 7th 2020 edited
     
    Lufttäthetens variation över året

    House 1
    124 m² (built in 2004). Insulated concrete slab on the ground and light wooden stud walls with mineral wool insulation. Air and vapor barrier is a 0.2 mm polyethylene foil. Exterior walls are built as follows from the outside in: 22 mm spontaneous wood panel, 22 mm spacer, windboard, 45 mm wooden joists and mineral wool, 145 mm wooden joists and mineral wool, 0.2 mm plastic foil and 13 mm plasterboard. However, we have not been able to take see detailed drawings of how the air and vapor tightness should be performed and we have not had opportunity to investigate this on site.

    Some of the major leaks we have noticed are above windows in the bay window in the kitchen, attachment of the carport roof at the stairs to the 2nd floor and attic hatch. Furthermore, several were noted at floor angles and at window sills. The house is at most 10% more leaky in winter than in summer (10% higher q50).

    House 2
    179 m² (built in 1993). Insulated concrete slab on the ground with underfloor heating coils and light wooden stud walls with mineral wool insulation (prefabricated). The air and vapor barrier is 0.15 mm polyethylene film. Exterior walls are built as follows from the outside in: 15 + 21 mm lid-wood panel, distance batten, 13 mm asphabo board, 240 mm wooden joists and mineral wool, 0.15 mm plastic foil and 9 mm byggboard. We have seen several drawings and construction details but not had opportunity to examine construction details on site.

    The largest single leak is found at the shaft for the chimney, which turns out to be both a leak from the underside of the mezzanine floor in the boiler room on the 1st floor, as cooling of the mezzanine floor, leakage in the floor angle and in the closet in the living room on the 2nd floor, cooling of the shaft wall on the 2nd floor and leakage in the roof angle in the living room and walk-in closet on the 2nd floor. Other types of leakage are mainly leakage in window sills, at / out electrical installations, roof angles, floor angles, around ventilation devices and at attic doors. [The house is at most 8% more leaky in winter than in summer (8% higher q50)].

    Apartment
    79 m² (built during 2013-2014) with a concrete frame. Exterior walls is built as follows from the outside in: plaster, 120 mm cellular insulation, 150 mm reinforced concrete, 120 mm cellular insulation, steel (studs?) and inner plaster. The 150mm gap between the insulation blocks is filled with insitu reinforced concrete. The air tightness for exterior walls is in the concrete and in various connection details such as window fasteners. We have not had the opportunity to examine construction details on site.

    We noted at measurement five in October was that the sealant at the inside window lining has begun to crack, which has led to local air leakage. Some of the major leaks we have noticed are the connection between the window frame and window frame, floor angle (can be the connection in the mezzanine floor in the outer wall and internal leakage within the building) and pipe shaft in the bathroom (internal leakage within the building). Furthermore, several air leaks were noted at floor angles and at windows between arches and frame. [It has] slightly deteriorated density over time. There has been a 6% decrease in concrete density(?) during the scarce year that the measurements are in progress. There is no correlation with relative moisture inside.

    General
    In wooden houses, there is a correlation between relative humidity inside the house and that of the building air tightness (Wahlgren, 2014). For [House 1] it is only when using instantaneous values ​​of the relative humidity indoors that the conformity becomes something worse. For [House 2] the best agreement with relative humidity indoors is obtained for averaging over two and three weeks. For both [houses] there is a poor correlation with temperatures inside and outside.

    A probable reason why the air density varies with the season in [Houses 1 & 2] is that there are relatively "superficial" air leaks (near the inside) that change with prevailing relative humidity in the air indoors and outdoors. An example of movements that cause leaks can be that a wooden bar, beam or board material in the construction near the hot side swells or shrinks against the plastic foil depending on how it relative humidity indoors is. If the shrinking material has the function of squeezing the plastic foil, this can create an air leak. It can also be the case that themselves the disc is the airtight layer (sometimes together with the surface treatment), which makes it leaks are also created in this case when the disc shrinks. However, it is not possible to exclude others reasons...

    To get a good and durable air tightness, the right products and solutions must be used. In a report from SP, Ylmén et al. (2012), it was found i.a. to show construction products is worse than others regarding age resistance and that some products were not very compatible with each other. An example is different dimensional stabilities of splicing tapes and foil products after accelerating aging testing. This caused air leaks through channels formed where tape and foil have contracted to varying degrees. Whether this affects the annual variation of the air tightness over the climate screen is uncertain.

    If the leakage varies by one order of magnitude as in the wooden houses in question this gives a small impact on energy use in most cases. [As a result of climate change] one should make sure to have a good one
    safety margin in terms of airtightness.

    One factor that has not been investigated in the project is how the building's ventilation system affects the airtightnesses. Different ventilation systems provide different pressure images in the building and thus different direction and speed of air flows through the climate shell. The air flows, in turn, affect the building and can be both moisturising and dehydrating. A building with natural ventilation could have a lower part of the building being dried out and an upper part of the building where the climate shell is moistened.


    An interesting RH link, though not very significant in impact (compared to studies of older homes that I've read), and not sure what 'disc' refers to, but the overall message is that airtightness is important, most leaks are at junctions, so get your details right.
    • CommentAuthorMike1
    • CommentTimeNov 7th 2020 edited
     
    Posted By: SimonDMy particular interest is how not necessarily how occupants’ everyday practices affect energy consumption of a building as I think given the research, that is a given, but rather how our relationship with both the building and immediate natural environment affect those practices, some of which we may not be aware of.

    And for me, the approach to simply provide a technical solution is inadequate. The same PHD suggests something similar:

    “.. the ability of these systems to provide adequate indoor air quality depends on many factors such as the existence of user friendly controls (Stevenson et al. 2013) maintenance of the system (Lowe & Johnston, 1997), performance (Kurnitski et al. 2007) and operation."
    I take a similar view; any technological system doesn't stop with the technology; it needs to include the people using it and the environment in which they, and it, operate.

    And now that homes really are becoming 'machines for living in', there are consequences that need consideration. You wouldn't expect to operate a car without taking lessons, nor run it without servicing, and you would expect it to come with a suitable user interface and easy-to-read handbook.
    •  
      CommentAuthordjh
    • CommentTimeNov 7th 2020
     
    Posted By: Mike1An interesting RH link, though not very significant in impact (compared to studies of older homes that I've read), and not sure what 'disc' refers to, but the overall message is that airtightness is important, most leaks are at junctions, so get your details right.

    Thanks for the translation, Mike. The study seems to be of three unremarkable houses - it's a pity they don't state the actual airtightness numbers as well as the percentage change. But they don't seem to have been built with any special care and the failings all seem to be at junctions as you say. I was going to suspect that there may have been no gaskets fitted under the sole plates, or problems with their fitting, but it seems like the problems were much more basic than that. I don't think the information tells us anything new, just reinforces the importance of details as you say.

    I found the abstract for one of his other papers 'Moderating Indoor Conditions with Hygroscopic Building Materials and Outdoor Ventilation' ASHRAE Transactions . 2004, Vol. 110 Issue 2, p804-819. It says: 'In general, increasing the ventilation has a stronger impact on the average indoor conditions than applying hygroscopic materials, but the impacts of ventilation and hygroscopic materials can be similar during certain operating conditions.' which seems reasonable to me. The other paper about numerical modelling that predicts the transfer of water vapor, CO2, and SF6 between the building envelope and air seems a little strange. Why would SF6 be considered?
    •  
      CommentAuthordjh
    • CommentTimeNov 7th 2020
     
    Posted By: SimonDI don’t mean all of this to become some evangelical rant, more that when it comes to ventilation, we’ve got a lot more to understand in terms of how it sits with the whole house design and those living within it, the energy actually consumed, health and comfort.

    Me neither, and I suspect we agree about many things but are just looking at them from different viewpoints. I'm sure there is more to learn about ventilation but an awful lot of money has been spent and research has been done it in many different contexts, so I'm fairly happy we know enough to make reasonable assumptions when designing our houses.

    I'm not convinced about humidity and hygroscopicity though. I think we understand humidity pretty well but I'm less convinced about our knowledge of hygroscopicity and how it interacts with other factors. We know enough to know that humidity can be dangerous, or just uncomfortable, and so the tendency is to simply design out those risks. Hence the prevalance of non-organic materials, for example, since they simply don't carry the same risks. I think you may find it interesting to read some of Tim Padfield's writing.

    For myself, having chosen to build one of the most hygroscopic houses I'm aware of, I didn't feel that taking additional risks with the ventilation strategy was sensible. And I'm not convinced there's that much to be gained from the possible alternatives, TBH.
    • CommentAuthorMike1
    • CommentTimeNov 8th 2020
     
    Posted By: djhThe other paper about numerical modelling that predicts the transfer of water vapor, CO2, and SF6 between the building envelope and air seems a little strange. Why would SF6 be considered?
    Good question., The only thing that I can spot in a quick Google search is a report from 2001 mentioning that that SF6 was used in double glazing in some countries - Mainly outside Europe, but Germany gets a mention (https://ec.europa.eu/clima/sites/clima/files/eccp/docs/eccp_wg_final_report_en.pdf)
    • CommentAuthorMike1
    • CommentTimeNov 8th 2020 edited
     
    Posted By: djhI'm not convinced about humidity and hygroscopicity though. I think we understand humidity pretty well but I'm less convinced about our knowledge of hygroscopicity and how it interacts with other factors. We know enough to know that humidity can be dangerous, or just uncomfortable, and so the tendency is to simply design out those risks.
    In addition, buildings built with hygroscopic material require their inhabitants to understand the nature of the building and how to maintain it. You wouldn't want them painting the walls with plastic paints, for example. And if it's difficult for people to understand what a MVHR unit does and how to operate and maintain it, despite being able to physically see it, how well will they cope with a building that looks like any other, but isn't?

    Of course that's not a problem if you're consciously self-building that way (at least while you still own it), but mass-market adoption could be trickier.

    BTW, in my area there are quite a few buildings - some of them 4 or 5 floors high - built of pisé (rammed earth), so very hygroscopic. I did consider buying one a couple of years ago, but after much research and some discussion on this board, I concluded that the scientific evidence on how to safely bring it up to modern thermal standards (particularly as it had a party wall with an unheated non-domestic building) wasn't strong enough. But if I had, it would certainly have had MVHR.
    • CommentAuthorSimonD
    • CommentTimeNov 8th 2020
     
    Posted By: djh
    Posted By: Mike1An interesting RH link, though not very significant in impact (compared to studies of older homes that I've read), and not sure what 'disc' refers to, but the overall message is that airtightness is important, most leaks are at junctions, so get your details right.

    Thanks for the translation, Mike. The study seems to be of three unremarkable houses - it's a pity they don't state the actual airtightness numbers as well as the percentage change.

    I found the abstract for one of his other papers 'Moderating Indoor Conditions with Hygroscopic Building Materials and Outdoor Ventilation' ASHRAE Transactions . 2004, Vol. 110 Issue 2, p804-819. It says: 'In general, increasing the ventilation has a stronger impact on the average indoor conditions than applying hygroscopic materials, but the impacts of ventilation and hygroscopic materials can be similar during certain operating conditions.' which seems reasonable to me. The other paper about numerical modelling that predicts the transfer of water vapor, CO2, and SF6 between the building envelope and air seems a little strange. Why would SF6 be considered?


    The Swedish study does provide the numbers and percentage changes, they just don't seem to come across in the translation. If I get the time, I'll translate those figures but it's likely to be a few days. I'll also make an effort to modify the nonsensical parts of the google translate output :smile:

    In terms of this hygroscopic/ventilation question, the conclusion from 'Potential for Hygroscopic Building Materials to Improve Indoor Comfort and Air Quality in the Canadian Climate 2004 ASHRAE' reaches a slighly different conclusion:

    "At a ventilation rate of 0.5 ach, the peak humidity is typically reduced by 10% to 25% RH. The reduction is slightly greater in Toronto than in Vancouver and Saskatoon. At a ventilation rate of 1 ach, hygroscopic materials have a smaller effect on the indoor humidity, and the reduction in the peak humidity typically varies from 5% to 10% RH.
    A comparison of the hygroscopic and nonhygroscopic materials using data from three-day test periods during humid weather in Toronto (June), cool weather in Vancouver (November), and cold weather in Saskatoon (January) further demonstrate the importance of hygroscopic materials. During the humid and cool weather, the hygroscopic materials improve the indoor conditions, but during the cold weather, the effect is minimal. An important result from the humid and cool test periods is that the comfort and air quality in a room with significant hygroscopic materials and a ventilation rate of 0.5 ach is nearly the same as that in a room with no hygroscopic materials and a ventilation rate of 1 ach. This indicates that buildings with a large amount of hygroscopic material may not need as much outdoor ventilation air as buildings with no hygroscopic material to provide a comparable thermal comfort and perceived air quality. However, the ventilation required to dilute pollutants is likely independent of the amount of hygroscopic material."

    So for me the relation between ventilation/hygroscopicity is still up for debate :bigsmile:


    Posted By: djh
    Posted By: SimonDI don’t mean all of this to become some evangelical rant, more that when it comes to ventilation, we’ve got a lot more to understand in terms of how it sits with the whole house design and those living within it, the energy actually consumed, health and comfort.

    Me neither, and I suspect we agree about many things but are just looking at them from different viewpoints.

    I'm not convinced about humidity and hygroscopicity though. I think we understand humidity pretty well but I'm less convinced about our knowledge of hygroscopicity and how it interacts with other factors. We know enough to know that humidity can be dangerous, or just uncomfortable, and so the tendency is to simply design out those risks. Hence the prevalance of non-organic materials, for example, since they simply don't carry the same risks. I think you may find it interesting to read some of Tim Padfield's writing.

    For myself, having chosen to build one of the most hygroscopic houses I'm aware of, I didn't feel that taking additional risks with the ventilation strategy was sensible. And I'm not convinced there's that much to be gained from the possible alternatives, TBH.


    Yes, I think we do agree and are coming from it from different directions.

    I'm fascinated by and I'm convinced by hygroscopicity in so far as it plays not just and important, but essential role within the whole system of a building as opposed to it being a solution, but I do think that our tendency to try to design out those risks often ends up detrimental, sometimes even over the very short term.

    There is an ancient fable from China about how a god tried to tame the elements, damming up the water for irrigation, only to cause some of the most catastrophic floods that destroyed the farming lands, causing famine. Obviously the moral of the story is to work with the elements as opposed to against them :smile:

    I appreciate your approach and decisions re your ventilation strategy. I'm using some fairly traditional and well tested building approaches in terms of timber frame etc. that I feel the freedom to explore the natural ventilation road and take on those inevitable experimental risks.

    Thanks for the heads up on Tim Padfield. I've just read his presentation on Breathability (https://conservationphysics.org/breath/breathability.html) and chuckled at part of his conclusion:

    "Finally, I want to emphasise that 'breathability' used as a universally good principle is as useless a way of evading understanding of the immediate situation as is 'sustainability' or 'ecological': words that lost their meaning as soon as they were adopted as buzzwords by right thinking people. Every situation has to be evaluated from a sound knowledge of physics."


    Posted By: Mike1In addition, buildings built with hygroscopic material require their inhabitants to understand the nature of the building and how to maintain it. You wouldn't want them painting the walls with plastic paints, for example. And if it's difficult for people to understand what a MVHR unit does and how to operate and maintain it, despite being able to physically see it, how well will they cope with a building that looks like any other, but isn't?


    I agree and find myself frustrated by, for example, the marketing literature of wood fibre insulation. Much is touted of their benefits, but there is nothing about considering the internal finish to get the most out of the products, thus people may just cover it all up in plastic paints. Maybe these companies are just concerned with the building fabric as opposed to the whole house, who knows. :confused:
    • CommentAuthorEd Davies
    • CommentTimeNov 8th 2020
     
    Posted By: Mike1You wouldn't expect to operate a car without taking lessons, nor run it without servicing, and you would expect it to come with a suitable user interface and easy-to-read handbook.
    Yes. It was interesting chatting with one of the BioRegional people [¹] about BedZED. They initially had a lot of problems with flats overheating because when it got a bit warm residents threw open the doors/windows to the glass atriums making the problem much worse. They put out a leaflet explaining the need to keep those openings closed in warm weather and this solved the problem. People will modify their behaviour when they understand what needs doing and why.

    [¹] http://tomchance.org/
    • CommentAuthorMike1
    • CommentTimeNov 8th 2020
     
    The hygroscopic debate & state of research remind me very much of the state of knowledge of how to design low energy buildings a few decades ago. Experiments with south-facing glazing and Trombe walls, solar porches, DIY solar-thermal panels, 'thermal mass', earth sheltering, passive stack ventilation and the like, particularly in the USA, Canada and Scandinavia, with interesting but often not very practical reports, sometimes lacking in scientific content.

    Trying to assemble a sensible collection of such ideas and technologies into a practical, affordable house that actually worked as expected in a particular climate was pretty challenging. That pretty much remained the case until the research by Bo Adamson and Wolfgang Feist eventually lead to the launch the Passive House Planning Package in 1998, which finally gave sufficiently predictable results.

    There must be scope for some researchers to do likewise and build a reliable model for hygroscopicity that can be readily and reliably applied in the real world.
    •  
      CommentAuthordjh
    • CommentTimeNov 8th 2020
     
    Posted By: SimonDAt a ventilation rate of 0.5 ach, the peak humidity is typically reduced by 10% to 25% RH. The reduction is slightly greater in Toronto than in Vancouver and Saskatoon. At a ventilation rate of 1 ach

    It's perhaps worth noting that even the lower of those two rates is higher than most people here feel is necessary or advisable. I've been told I'm overventilating when I admit that I sometimes set the MVHR around 0.3 ACH. I suppose that means hygroscopic construction is even more important to consider.

    Posted By: Mike1There must be scope for some researchers to do likewise and build a reliable model for hygroscopicity that can be readily and reliably applied in the real world.

    I think part of the difficulty in doing this is its susceptibility to minor-seeming details. What paint has been used? Are there downlighters in the ceiling, and if so are they sealed? Was the plasterboard paper-faced? etc etc ad nauseam
    • CommentAuthortony
    • CommentTimeNov 8th 2020
     
    Guessing - yes 65% saving but in Canada near 100% as mostly hydro electric

    Cost only 35% saving on fuel varying up to zero saving depending on how well designed

    Capital cost can be high
Add your comments

    Username Password
  • Format comments as
 
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press