Navitron Renewable Energy and Sustainability Forum

Green Building and Design => Green Construction/DIY => Topic started by: Greenbeast on September 19, 2017, 08:35:23 AM



Title: New house design stage
Post by: Greenbeast on September 19, 2017, 08:35:23 AM
I've played the game of ideal house-build before, but now i'm looking at it for planning permission submission next year.
There's lots to tackle, my first two queries are so i can start to get a decent 3d plan together.
I'm looking to have a covered porch along the front (south-facing) elevation, to prevent over-insolation of the glazed portion during the hot summer months. Is there a calculator/method out there so that i can work out the ideal extension/height of the cover to get the best out of passive solar heating?

Not looked at building materials in a while. I think, although i would loved rammed earth, that's never going to pass muster with the boss, so i reckon we're looking at timber frame/SIPS, what sort of wall thickness should i be looking at. Want to get it right early on, insulation-wise, seems mental not to.


Title: Re: New house design stage
Post by: dhaslam on September 19, 2017, 09:15:48 AM
I have an overhang of about one metre on the south side.   Midday sun is just coming into the rooms now which is about right.    East and west windows are the ones to be careful of because the sun comes shines directly in.     



Title: Re: New house design stage
Post by: Greenbeast on September 19, 2017, 09:24:51 AM
Thanks, whereabouts in the country are you? What sort of height is the overhang?

The west is shaded by trees, the east we'll have to watch, there is a tree-line but maybe not enough shade


Title: Re: New house design stage
Post by: A.L. on September 19, 2017, 09:59:32 AM
hello FWIW,

- for shading of south facing windows ideally draw two lines, one at ((90-latitude)-23.5) up from horizontal at lintel and one at ((90-latitude)+23.5) from windowsill. Where they intersect gives full exposure on Dec21 and no exposure on Jun21

- for a U-value of 0.12 with fibrous type insulation in a timber frame you are looking at a total thickness of 350mm for a render finish or perhaps 400mm for a rain-screen construction


Title: Re: New house design stage
Post by: Fionn on September 19, 2017, 10:33:45 AM
Dhaslam is spot on, it's definitely the East and West that are tricky to shade effectively. South is very easy.
Personally I'd go with PIR fill and a further PIR wrap outside if going timber frame, should reduce the wall thickness quite a bit over fibrous insulation and the insulation will actually help stiffen the wall a lot - not that anybody will include it in any calculations obviously.
Picking the rainscreen is the tricky bit!


Title: Re: New house design stage
Post by: dhaslam on September 19, 2017, 10:57:23 AM
Thanks, whereabouts in the country are you? What sort of height is the overhang?


Latitude is 53 degrees Irish Midlands.   The  overhang supports the roof with pillars so shading starts at chute level.



Title: Re: New house design stage
Post by: Warble on September 19, 2017, 01:12:50 PM
In a new house wall thickness is not so important so I would use an I-beam timber frame with fibre batt insulation. I wouldn't use PIR because it is expensive, highly combustible and not sustainable.


Title: Re: New house design stage
Post by: todthedog on September 19, 2017, 02:47:24 PM
Have a look at this GB

http://inhabitat.com/prefab-prispa-by-romanias-solar-decathlon-team-produces-20-more-energy-than-it-uses/

Not far off what Mrs T and I were looking at building a couple of years back.
I have contact details if wanted


Title: Re: New house design stage
Post by: Fionn on September 19, 2017, 05:57:50 PM
Here in Ireland people are obsessed with using traditional cavity wall construction using 4in blocks for the inner and outer leaf. They are using cavities up to 250mm now to get the desired u-value which leaves you with a wall a good half metre thick.
I think they look ridiculous myself to be honest, it's like going back to living in medieval castles.
I wouldn't be overly concerned with the flammability of PIR in a domestic setting. Given that it will be encased beind OSB on the outside and OSB + plasterboard inside, the house will be long gone before it goes on fire.
Grenfell a different kettle of fish entirely.


Title: Re: New house design stage
Post by: djh on September 19, 2017, 10:17:43 PM
- for shading of south facing windows ideally draw two lines, one at ((90-latitude)-23.5) up from horizontal at lintel and one at ((90-latitude)+23.5) from windowsill. Where they intersect gives full exposure on Dec21 and no exposure on Jun21

I agree with these sums but be aware that they may not help you much. I have two large windows on the ground floor that face south. The original design had a brise soleil across the top of them, but for various reasons it wasn't fitted. My plan changed to installing a pergola instead, with deciduous vegetation (i.e. grape vines) to provide shade. But I still haven't fitted that after two years. My problems are (1) in winter and up to sometime in April I want as much sun as possible; from later in April through the summer I would ideally have some shading, but my wife and I enjoy the warmth and only start to worry if it approaches 28C, so (2) working out the best position turns out to be a different problem than that solved by the equations. (3) Summer bypass on the MVHR is really important to helping temperature regulation, and I can't help thinking that some kind of adjustable external shading might be better than a brise soleil or pergola for the same reason - active control.

I have large roof overhangs (mainly to keep the straw bale walls drier) that shade the upstairs windows. The house was designed with PHPP to PH standard so our east and west facing windows are reasonably sized and the north facing one is lonely! East windows are not as bad for overheating as west ones, so you're in luck.

For design ideas for a south-facing enclosed porch, I'd suggest the best place to start might be to look at Hockerton.

I'm with warble - my walls are half a metre thick and I and others think they look good. Long before Grenfell I decided not to use PIR/PUR in my house because of the toxic smoke risk. I did use EPS underfloor and in the sun room outside the thermal envelope, and I would have used phenolic if necessary. I used mineral wool in internal walls and first floor void and some wood fibre around windows. But apart from straw bales my first choice insulation has to be cellulose, which we used for the roof. It's good acoustically and humidity-wise as well as helping airtightness and being easy to get installed.

I'd go with a good timber frame company rather than SIPs, myself.


Title: Re: New house design stage
Post by: Greenbeast on September 20, 2017, 07:33:11 AM
Thank you very much for your thoughts :)
Lots to consider


Title: Re: New house design stage
Post by: pdf27 on September 20, 2017, 08:22:13 AM
I'm going through the process of adding another storey to my house at the moment, aiming for the EnerPHit standard which essentially means that the upper storey is to PH standard and the lower storey is a bit compromised by the existing structure. A few thoughts so far:
  • Glazing orientation isn't that critical - we're mostly north facing (forced by the house) with no shading on the south orientation, and aren't having to work too hard to hit EnerPHit - and PHPP shows virtually no overheating risk. Don't concentrate on sorting the glazing orientation out at the expense of it working as a house.
  • Strong preference for cellulose-insulated timber frame here - total wall thickness ends up as about the same as blockwork/foam, but being that timber frame tends to be factory built that fits with our likely timescales (currently living in the house, want to minimise the time we're homeless.
  • It's questionable how much it's worth concentrating on the last little bit of performance, and whether overheating is really such a problem - for new build then heat pumps make a lot of sense, particularly if you have the room to go ground-source. That makes adding in cooling really, really cheap and even a little bit of extra heat in winter doesn't cost much. Have a think about your preferred balance of generation versus reduced consumption - particularly with heat pumps it isn't at all clear to me that dealing with overheating purely by house design is necessarily the right route. Even without active cooling PHPP has our house which is mostly North/South has virtually no overheating, with the insulation helping a lot here - shading to reduce this further would have a big visual and potentially cost impact, to deal with something that active cooling does better (e.g. providing overnight cooling when the outside air temperature is 30C for that one day a year/


Title: Re: New house design stage
Post by: Greenbeast on September 20, 2017, 08:57:19 AM
I'm going through the process of adding another storey to my house at the moment, aiming for the EnerPHit standard which essentially means that the upper storey is to PH standard and the lower storey is a bit compromised by the existing structure. A few thoughts so far:
  • Glazing orientation isn't that critical - we're mostly north facing (forced by the house) with no shading on the south orientation, and aren't having to work too hard to hit EnerPHit - and PHPP shows virtually no overheating risk. Don't concentrate on sorting the glazing orientation out at the expense of it working as a house.
  • Strong preference for cellulose-insulated timber frame here - total wall thickness ends up as about the same as blockwork/foam, but being that timber frame tends to be factory built that fits with our likely timescales (currently living in the house, want to minimise the time we're homeless.
  • It's questionable how much it's worth concentrating on the last little bit of performance, and whether overheating is really such a problem - for new build then heat pumps make a lot of sense, particularly if you have the room to go ground-source. That makes adding in cooling really, really cheap and even a little bit of extra heat in winter doesn't cost much. Have a think about your preferred balance of generation versus reduced consumption - particularly with heat pumps it isn't at all clear to me that dealing with overheating purely by house design is necessarily the right route. Even without active cooling PHPP has our house which is mostly North/South has virtually no overheating, with the insulation helping a lot here - shading to reduce this further would have a big visual and potentially cost impact, to deal with something that active cooling does better (e.g. providing overnight cooling when the outside air temperature is 30C for that one day a year/

Interesting thank you.

We do have plenty of space for gshp actually. I kinda hadn't considered it because my parents have not had the best time with it. Is it worth while (I really, really hope the house will have a good solar array)?


Title: Re: New house design stage
Post by: Greenbeast on September 20, 2017, 09:03:01 AM
re:GSHP, works better with UFH no?
Concerned about UFH because of the dogs, have always assumed i'd put it in a house i'd build until i met my g/f with her pack


Title: Re: New house design stage
Post by: marshman on September 20, 2017, 09:04:19 AM
As a bit of a "curved ball" what about a bit of Thermal Mass?    I am all for highly insulated, controlled ventilation etc. but in my experience you get a more stable and just as importantly "comfortable" atmosphere in a house if it has a bit (ok a lot) of thermal mass. Obviously this works better if the house is occupied 24/7. My thinking, (no actual hard facts or figures so please discuss/dismiss as you feel fit), is in the summer the thermal mass limits the day time temp rise whilst giving it up in the evenings, works well in the "shoulder" months. The building is incapable of sudden temperature changes, so after a cold frosty night in the winter the house is still warm in the morning.  The disadvantage of a lot of thermal mass is it can take several days to warm the house if you go a way for a few days, but now we have a GSHP running I just leave it "ticking over" 24/7.

The house we have is an old farmhouse with thick walls and a massive central brick chimney - admittedly you would not do a new build this way, but it is well insulated with an inner skin of 5" (125mm) thermal (celcon) blocks and a foam filled cavity. The external wall is 12 to 18" solid brick. It is a large house (over 200 m sq) yet the heating from the GSHP uses about 1800kWh of electric, per year (approx 7200kWh heat). We do have a woodburner in the north facing lounge which contributes a bit but not very much.

Just a thought.

Roger


Title: Re: New house design stage
Post by: Greenbeast on September 20, 2017, 09:19:26 AM
As a bit of a "curved ball" what about a bit of Thermal Mass?    I am all for highly insulated, controlled ventilation etc. but in my experience you get a more stable and just as importantly "comfortable" atmosphere in a house if it has a bit (ok a lot) of thermal mass. Obviously this works better if the house is occupied 24/7. My thinking, (no actual hard facts or figures so please discuss/dismiss as you feel fit), is in the summer the thermal mass limits the day time temp rise whilst giving it up in the evenings, works well in the "shoulder" months. The building is incapable of sudden temperature changes, so after a cold frosty night in the winter the house is still warm in the morning.  The disadvantage of a lot of thermal mass is it can take several days to warm the house if you go a way for a few days, but now we have a GSHP running I just leave it "ticking over" 24/7.

The house we have is an old farmhouse with thick walls and a massive central brick chimney - admittedly you would not do a new build this way, but it is well insulated with an inner skin of 5" (125mm) thermal (celcon) blocks and a foam filled cavity. The external wall is 12 to 18" solid brick. It is a large house (over 200 m sq) yet the heating from the GSHP uses about 1800kWh of electric, per year (approx 7200kWh heat). We do have a woodburner in the north facing lounge which contributes a bit but not very much.

Just a thought.

Roger

Indeed, as i said i would love to have rammed earth, that really speaks to me from many levels, but the OH will not go for it ("you're not building our house from mud")
As we never go away the issue of 'reheating' the mass is not a concern


Title: Re: New house design stage
Post by: marshman on September 20, 2017, 09:20:10 AM
re:GSHP, works better with UFH no?
Concerned about UFH because of the dogs, have always assumed i'd put it in a house i'd build until i met my g/f with her pack

I have a GSHP with UFH. The GSHP was install just under 2 years ago - wish I had done it sooner.  The key is good design, properly sized ground loops, and run it 24/7 to keep floor temps very low - a well designed system should not have "hot floors" so nothing to upset the dogs. The only time we notice that our floor is actually warm is in the kitchen during a really cold spell, even then it is just pleasant. All other times you just notice that it doesn't feel cold if you walk on it with bare feet. All the other rooms have thick carpet so you can't seem to feel it at all.  The average temp of the floor is only just above room temperature. I don't have any room stats, zone valves or any of that complication, just one circulating pump and a buffer tank, it all runs from the outside stat and the controller on the heat pump. It just controls the average temp of the circulating water in the UFH based on the rate of heat loss from it. The flow to each room has been gradually tweaked to give the correct temperature in each room (basically warm in the living areas and cooler in the bedrooms).  

My view is on the heating side is keep it simple, there is nothing to go wrong bar the circulating pump (Grundfos Alpha running at its very lowest auto setting - approx 7W). Trouble is it will be very hard to convince a heating design engineer to throw all the bells and whistles away (room stats, zone valves etc.) I suspect you will also need a degree of thermal in the building to "smooth" the temperature - see my earlier post.

Roger  


Title: Re: New house design stage
Post by: A.L. on September 20, 2017, 09:52:02 AM
hello again,

re:GSHP, works better with UFH no?
Concerned about UFH because of the dogs, have always assumed i'd put it in a house i'd build until i met my g/f with her pack

-what's your worry regarding dogs? can't think of one - floor of a heavily insulated house is not likely to exceed 24C


Title: Re: New house design stage
Post by: Greenbeast on September 20, 2017, 09:54:01 AM
hello again,

re:GSHP, works better with UFH no?
Concerned about UFH because of the dogs, have always assumed i'd put it in a house i'd build until i met my g/f with her pack

-what's your worry regarding dogs? can't think of one - floor of a heavily insulated house is not likely to exceed 24C

They'll have no respite from the heat if it's too much, i wonder if we would like to spend hours laying on a 24C floor, i suspect not


Title: Re: New house design stage
Post by: smegal on September 20, 2017, 10:16:04 AM
hello again,

re:GSHP, works better with UFH no?
Concerned about UFH because of the dogs, have always assumed i'd put it in a house i'd build until i met my g/f with her pack

-what's your worry regarding dogs? can't think of one - floor of a heavily insulated house is not likely to exceed 24C

They'll have no respite from the heat if it's too much, i wonder if we would like to spend hours laying on a 24C floor, i suspect not

They can jump on the sofa/bed.


Title: Re: New house design stage
Post by: Greenbeast on September 20, 2017, 10:25:33 AM
all 8 of them? the biggest weighs 60kg.  :hysteria

 :)


Title: Re: New house design stage
Post by: djs63 on September 20, 2017, 12:40:23 PM
The dogs must give a fair bit of heat!
And a tiled floor would conduct ufh best and be easy to clean dig hairs and foot prints.  We have Gshp fir 8 years, excellent.


Title: Re: New house design stage
Post by: Greenbeast on September 20, 2017, 01:04:46 PM
The dogs must give a fair bit of heat!

i wonder if there's a heat loss calc that takes them into account...  ;D ;D


Title: Re: New house design stage
Post by: Fionn on September 20, 2017, 01:18:11 PM
Allow about 1W per kg of dog I reckon  ;D


Title: Re: New house design stage
Post by: djh on September 20, 2017, 08:01:16 PM
Quote from: pdf27
Glazing orientation isn't that critical - we're mostly north facing (forced by the house) with no shading on the south orientation, and aren't having to work too hard to hit EnerPHit - and PHPP shows virtually no overheating risk. Don't concentrate on sorting the glazing orientation out at the expense of it working as a house.

In our build it was very critical. Perhaps that's a difference between EnerPHit and PH level, or just some difference between the overall designs. If you have most windows with a northerly aspect, then I'd be very surprised if you did have any overheating risk, but most people try to increase solar gain more.

Quote from: greenbeast
i wonder if we would like to spend hours laying on a 24C floor

We spend all summer lying on a bed at that temperature or more at times. We find it very pleasant.

The dogs must give a fair bit of heat!
i wonder if there's a heat loss calc that takes them into account...  ;D ;D

The usual rule of thumb is 50 W for a dog, 100 W for a human, 5 W for a cat 0.5 W for a mouse. All a bit less when inactive. PHPP takes account of human occupants; I don't remember about dogs.


Title: Re: New house design stage
Post by: pdf27 on September 20, 2017, 08:25:34 PM
We do have plenty of space for gshp actually. I kinda hadn't considered it because my parents have not had the best time with it. Is it worth while (I really, really hope the house will have a good solar array)?
It is certainly my preferred option if I can make the budget work. As a solution it is more efficient, quieter and more robust than an air-source heat pump, and both are preferable to gas.

They'll have no respite from the heat if it's too much, i wonder if we would like to spend hours laying on a 24C floor, i suspect not
PH is limited to 10W/m2 in extremely cold weather, the predictions for my EnerPHit build are about 14W/m2. A screeded floor with tiles on top will provide 60W/m2 of heating if the water enters at 40C and leaves at 30C (http://www.johnguest.com/wp-content/uploads/2014/07/UFH-Tech-Doc-Z2105-387-0914WEB.pdf) (i.e. an average of 15C warmer than the air - 4W/C). That means a 24C floor would only occur in an EnerPHit house at the design low temperature (i.e. when it's properly brass monkeys outside - at which point the dogs would probably rather appreciate a warm floor to lie on), and never at all in a PassivHaus.

In our build it was very critical. Perhaps that's a difference between EnerPHit and PH level, or just some difference between the overall designs. If you have most windows with a northerly aspect, then I'd be very surprised if you did have any overheating risk, but most people try to increase solar gain more.
I suspect so - in the PHPP report the EnerPHit option has a 0.34% risk of overheating, the Passivhaus option has a 3.4% risk of overheating despite lower solar gains - it looks like the whole thing becomes significantly harder to balance as the energy consumption goes down. The thing is, the difference between the two is only 9 kWh/m2/year of heat - or about 300 kWh of electricity supplied to a good GSHP. The OP was talking about self-design rather than getting it modelled up, so I was assuming that he was more at the EnerPHit performance level than the PH level.


Title: Re: New house design stage
Post by: Greenbeast on September 21, 2017, 09:43:39 AM
Thanks for that. Gives me plenty to think about.


Title: Re: New house design stage
Post by: djh on September 21, 2017, 08:58:36 PM
The thing is, the difference between the two is only 9 kWh/m2/year of heat - or about 300 kWh of electricity supplied to a good GSHP.

The difference between the PH and EnerPHit limits is actually 10 kWh/m/a (difference between 25 kWh/m/a and 15 kWh/m/a) but that's neither here nor there.

More relevant is that there's no way I could ever justify the capital cost of a GSHP with my heat demand. I couldn't even justify the costs of a gas boiler, so I just have an electric post heater. At some stage I may consider an ASHP, depending on how circumstances change, but it's not on the horizon yet.


Title: Re: New house design stage
Post by: pdf27 on September 22, 2017, 07:33:13 AM
The difference between the PH and EnerPHit limits is actually 10 kWh/m/a (difference between 25 kWh/m/a and 15 kWh/m/a) but that's neither here nor there.
That was taken from the options I was given for our build - which came out as 23 or 14 kWh/m2/year - you're right, I should have quoted from the standard though.

More relevant is that there's no way I could ever justify the capital cost of a GSHP with my heat demand. I couldn't even justify the costs of a gas boiler, so I just have an electric post heater. At some stage I may consider an ASHP, depending on how circumstances change, but it's not on the horizon yet.
This is the one area I don't really agree with PHI - the root of the 15 kWh/m2/year is actually in the alternative standard of 10 W/m2 at the design low temperature, itself set by the amount of heat which could be delivered by ventilation air. So if you set a design target which means that the heat can be delivered by ventilation air only, it should be hardly surprising that a system to heat this ventilation air is the cheapest. For me however the correct target should be a primary energy one - which means the standard ought to be agnostic about whether a house uses 5kW of heat delivered by a heat pump consuming 1kW, or 1kW of heat delivered by a post heater consuming 1kW. The optimum balance between insulation and heat pump would then be varied depending on the site and personal preferences - on our site, for instance, hitting the 15 kWh/m2/year target is virtually impossible but were we to use a heat pump to generate the 25 kWh/m2/year heat then we would probably end up consuming less primary energy than you do.
Ultimately the real attraction of PH for me is in the rigorous building physics underlying the model, not necessarily in the somewhat arbitrary standard used.


Title: Re: New house design stage
Post by: Bodidly on September 22, 2017, 07:49:58 AM
hello again,

re:GSHP, works better with UFH no?
Concerned about UFH because of the dogs, have always assumed i'd put it in a house i'd build until i met my g/f with her pack

-what's your worry regarding dogs? can't think of one - floor of a heavily insulated house is not likely to exceed 24C

They'll have no respite from the heat if it's too much, i wonder if we would like to spend hours laying on a 24C floor, i suspect not

We have GSHP,UFH and a dog and yes initially when we first got her she would avoid the UFH by sleeping in the doorway alcove as I did not lay any pipes there due a thermal bridging issue. She soon changed her habits and now seeks out warm spots like a cat  :D > Usual spot is right in front of the wood burner. Doubt the floor ever gets much hotter than 25C as the circulating water never goes over 30C


Title: Re: New house design stage
Post by: Greenbeast on September 22, 2017, 10:22:09 AM
hello again,

re:GSHP, works better with UFH no?
Concerned about UFH because of the dogs, have always assumed i'd put it in a house i'd build until i met my g/f with her pack

-what's your worry regarding dogs? can't think of one - floor of a heavily insulated house is not likely to exceed 24C

They'll have no respite from the heat if it's too much, i wonder if we would like to spend hours laying on a 24C floor, i suspect not

We have GSHP,UFH and a dog and yes initially when we first got her she would avoid the UFH by sleeping in the doorway alcove as I did not lay any pipes there due a thermal bridging issue. She soon changed her habits and now seeks out warm spots like a cat  :D > Usual spot is right in front of the wood burner. Doubt the floor ever gets much hotter than 25C as the circulating water never goes over 30C

Thanks for your experience in the matter!


Title: Re: New house design stage
Post by: Fionn on September 22, 2017, 10:36:49 AM
Another tip is to run your UFH pipes as tightly spaced as is practical - 150mm maximum centres ideally.
Yes you will use more pipe, but pipe is cheap and the increased rate of heat transfer to the slab will allow you run a lower flow temperature for improved COP.


Title: Re: New house design stage
Post by: djh on September 22, 2017, 04:34:24 PM
This is the one area I don't really agree with PHI - the root of the 15 kWh/m2/year is actually in the alternative standard of 10 W/m2 at the design low temperature, itself set by the amount of heat which could be delivered by ventilation air. So if you set a design target which means that the heat can be delivered by ventilation air only, it should be hardly surprising that a system to heat this ventilation air is the cheapest.

Well, yes, but you can heat the ventilation air with a gas boiler or heat pump. But they both have a greater cost and greater maintenance bills than a simple electric heater.

Quote
For me however the correct target should be a primary energy one - which means the standard ought to be agnostic about whether a house uses 5kW of heat delivered by a heat pump consuming 1kW, or 1kW of heat delivered by a post heater consuming 1kW. The optimum balance between insulation and heat pump would then be varied depending on the site and personal preferences - on our site, for instance, hitting the 15 kWh/m2/year target is virtually impossible but were we to use a heat pump to generate the 25 kWh/m2/year heat then we would probably end up consuming less primary energy than you do.

I think a heat pump with an SPF of 5 is still fairly unusual, but perhaps I'm out of date. There are problems with basing a standard on primary energy given that it gets used for DHW production and many other things besides space heating and that there are many different ways of measuring primary energy depending on what fuel it is, how that fuel is used, whether it's supplied externally or from the site (e.g. solar, wind or hydro). In fact I was lucky that PHI have updated their PE calculation to a PER calculation, since previously it had been almost impossible to certify a passivhaus with an entirely resistive electric heating scheme. So I would have been forced to buy a heat pump, perhaps a 'combined unit'.

Quote
Ultimately the real attraction of PH for me is in the rigorous building physics underlying the model, not necessarily in the somewhat arbitrary standard used.

Yes, it's the basis of the model, which appears to be more scientifically based and less politically influenced than national standards, that attracted me to it in the first place. But the additional quality control and quality assurance that comes from the certification process is also part of it for me. I'm fairly sure that a certified house has actually been built to match the design documents that were used to perpare the certification spreadsheet. It's unlikely that insulation has been left out or just left still bagged up in the loft, for example; the construction photos would make that very difficult. The component certificates for my windows and so forth and the installation certificate for the blown-in warmcel all reassure me that it was built properly. Ultimately, being on site every day is the best way to know, but certificates and tracability provide an objective measure.


Title: Re: New house design stage
Post by: pdf27 on September 22, 2017, 05:54:10 PM
Well, yes, but you can heat the ventilation air with a gas boiler or heat pump. But they both have a greater cost and greater maintenance bills than a simple electric heater.
Indeed - if you're heating with ventilation air then an electric heater is the logical way of doing it. Where I disagree with them is the assumption that heating with ventilation air is particularly desirable - it works for a particular occupant density, climate and insulation level, but I'm not convinced that designing a standard around it is particularly desirable. All it really saves is a few radiators in some (not all) rooms - which seems to be a fairly modest benefit to me.

I think a heat pump with an SPF of 5 is still fairly unusual, but perhaps I'm out of date.
Unusual but not unknown - and more importantly it's easier to do the sums with 5:1 than 4.6:1  ;D

There are problems with basing a standard on primary energy given that it gets used for DHW production and many other things besides space heating and that there are many different ways of measuring primary energy depending on what fuel it is, how that fuel is used, whether it's supplied externally or from the site (e.g. solar, wind or hydro). In fact I was lucky that PHI have updated their PE calculation to a PER calculation, since previously it had been almost impossible to certify a passivhaus with an entirely resistive electric heating scheme. So I would have been forced to buy a heat pump, perhaps a 'combined unit'.
Thing is, they've had a primary energy standard of some sort all along - the use of PER has made it rather more rigorous, but it isn't a new idea. When you look at the impact of a house on the environment, it's primary energy that has an impact. I wouldn't get rid of a heat demand calculation at all - doing it and setting a standard is going to be required for comfort reasons - but the 15 kWh/m2/year or 10W/m2 standard don't make sense as the correct place to put a stake in the ground for me: I'd sooner see a slightly higher W/m2 standard, set by evidence of comfort levels, and keep the PER limits and maybe emphasise them a bit more.
DHW production is a pretty important point though - PH is at the stage where DHW is a bigger energy user than space heating, but the emphasis is still on the space heating target: since DHW use is limited to a few appliances and there are established ways to economise on it's use, this makes little sense to me. It comes out in the wash of the PER calculation at the moment, but I'd sooner see it emphasised a bit more since it and plug loads are the main consumers.


Title: Re: New house design stage
Post by: djh on September 22, 2017, 09:33:58 PM
"Thing is, they've had a primary energy standard of some sort all along - the use of PER has made it rather more rigorous, but it isn't a new idea."

Indeed but the problems with defining and measuring it and linking it to a building rather than an occupant's lifestyle explain to some extent why it's never been a primary criterion. It moves away from a simple 'fabric first' mentality and towards the monstrosity that was CSH.


Title: Re: New house design stage
Post by: acresswell on January 06, 2018, 10:13:41 PM

We have GSHP,UFH and a dog and yes initially when we first got her she would avoid the UFH by sleeping in the doorway alcove as I did not lay any pipes there due a thermal bridging issue. She soon changed her habits and now seeks out warm spots like a cat  :D > Usual spot is right in front of the wood burner. Doubt the floor ever gets much hotter than 25C as the circulating water never goes over 30C

Realise this is an old thread, but I'd second Bodidly...  our dog loves the UFH.  We have a mud room to store coats and wellies.  I tend to leave the UFH switched off in there (so we don't lose too much heat when the door is opened). We tried putting a dog bed in there but she never used it, preferring to sleep on the hard floor right next to the UFH manifold.  We also have our UFH pipes closely spaced and run the UFH at a low temperature, so the floor is probably never more than 25-30 degrees. I don't know what doggy body temperature is, but if we assume it's something like humans at 37 degrees, lying on a floor at 30 degrees would still be cooler than lying under a pile of pack-mates.

My other little tip (nothing to do with UFH) is that if you have any corner of a wall protruding into a room, try rounding it off, or measuring back about 2-2.5" from each corner and then cutting it off at 45 degrees. As long as you know in advance and include a bit of steel bracket inside the wall, it's still perfectly strong, but it's surprising how much difference it makes to how big the space feels, and how much more natural light can get around the room.  I reckon the only down side is that it's a tiny bit harder to fit the skirting board!


Title: Re: New house design stage
Post by: camillitech on January 07, 2018, 05:02:07 AM

My other little tip (nothing to do with UFH) is that if you have any corner of a wall protruding into a room, try rounding it off, or measuring back about 2-2.5" from each corner and then cutting it off at 45 degrees. As long as you know in advance and include a bit of steel bracket inside the wall, it's still perfectly strong, but it's surprising how much difference it makes to how big the space feels, and how much more natural light can get around the room.  I reckon the only down side is that it's a tiny bit harder to fit the skirting board!

Now, we have quite a few 'corners' like this in our house, though more like 6" and I didn't like them on the plans (neither did my builder) but we kept them and I'm glad we did. As for UFH heating and dogs, in a well insulated house with 8 of them you'll only ever need it in the bathroom. The dogs will be just fine. We've only 1 dog so heat the living area as well but when the family turn up for a couple of weeks with more dogs and bodies the heating rarely comes on and folk start opening windows.


Title: Re: New house design stage
Post by: Greenbeast on January 10, 2018, 08:31:04 PM
Thanks guys!


Title: Re: New house design stage
Post by: gb484 on February 25, 2018, 10:57:36 AM
post and beam with hempcrete: https://www.youtube.com/watch?v=FcctSvVFheA&t=30s