Passive house requirements for new build
Discussion
I have been looking at the requirements for building a passive house to see how viable it is for a new build I am considering. It seems new materials in the past few years have made it easier to achieve the requirements but one of them is puzzling me as to what it means:
The primary energy usage requirement of less than 120 kWh/m^2/year (first off, being pedantic, why isn't this expressed as kW/m^2?). My understanding is that this primary energy must cover heating, hot water, lighting, cooking, fridge, freezer dish washer etc. It equates to over 20,000kWh per year for the approximately 180m^2 house I would like to build. This is rather a lot more energy than my current inefficient old house of similar size uses annually, and a passive house will be much easier to heat. This is where a large chunk of the old house energy budget is spent. I must be misunderstanding something here - can anyone explain what I am not accounting for?
I've tried looking at the PHPP demo but suspect I really need the instructions to get a clear answer.
Thanks.
The primary energy usage requirement of less than 120 kWh/m^2/year (first off, being pedantic, why isn't this expressed as kW/m^2?). My understanding is that this primary energy must cover heating, hot water, lighting, cooking, fridge, freezer dish washer etc. It equates to over 20,000kWh per year for the approximately 180m^2 house I would like to build. This is rather a lot more energy than my current inefficient old house of similar size uses annually, and a passive house will be much easier to heat. This is where a large chunk of the old house energy budget is spent. I must be misunderstanding something here - can anyone explain what I am not accounting for?
I've tried looking at the PHPP demo but suspect I really need the instructions to get a clear answer.
Thanks.
According to the Passive House Institute the requirements are:
1. The Space Heating Energy Demand is not to exceed 15 kWh per square meter of net living space (treated floor area) per year or 10 W per square meter peak demand.
In climates where active cooling is needed, the Space Cooling Energy Demand requirement roughly matches the heat demand requirements above, with an additional allowance for dehumidification.
2. The Renewable Renewable Primary Energy Demand (PER, according to PHI method), the total energy to be used for all domestic applications (heating, hot water and domestic electricity) must not exceed 60 kWh per square meter of treated floor area per year for Passive House Classic. .
http://www.passiv.de/en/02_informations/02_passive...
1. The Space Heating Energy Demand is not to exceed 15 kWh per square meter of net living space (treated floor area) per year or 10 W per square meter peak demand.
In climates where active cooling is needed, the Space Cooling Energy Demand requirement roughly matches the heat demand requirements above, with an additional allowance for dehumidification.
2. The Renewable Renewable Primary Energy Demand (PER, according to PHI method), the total energy to be used for all domestic applications (heating, hot water and domestic electricity) must not exceed 60 kWh per square meter of treated floor area per year for Passive House Classic. .
http://www.passiv.de/en/02_informations/02_passive...
robemcdonald said:
You may be better off looking at just following the principle.
This I have heard from other people too. I may well just follow the principle because it does look to be a coherent and sensible set of aims (apart from the primary power usage one I am clearly not understanding!) and be happy to end up with a house that exceeds the current self build requirements. It does seem like a good idea to achieve the passive house standard for insulation etc since every modern house I have seen has needed mechanical ventilation for air quality, so why not try to make it do the heating and cooling as well to reduce complexity?
I would like to understand the primary power requirement though!
Outline spec from here:
http://www.passivhaus.org.uk/standard.jsp?id=18
Edited by dnb on Monday 22 August 22:41
dnb said:
This I have heard from other people too. I may well just follow the principle because it does look to be a coherent and sensible set of aims (apart from the primary power usage one I am clearly not understanding!) and be happy to end up with a house that exceeds the current self build requirements.
It does seem like a good idea to achieve the passive house standard for insulation etc since every modern house I have seen has needed mechanical ventilation for air quality, so why not try to make it do the heating and cooling as well to reduce complexity?
I would like to understand the primary power requirement though!
Outline spec from here:
http://www.passivhaus.org.uk/standard.jsp?id=18
I comment on all aspects, but for vent you will need a mechanical vent with heat recovery.It does seem like a good idea to achieve the passive house standard for insulation etc since every modern house I have seen has needed mechanical ventilation for air quality, so why not try to make it do the heating and cooling as well to reduce complexity?
I would like to understand the primary power requirement though!
Outline spec from here:
http://www.passivhaus.org.uk/standard.jsp?id=18
Edited by dnb on Monday 22 August 22:41
OP: be careful what you wish for. "B" rating is easier to achieve, and you'll be permitted to have the all important PH bifold doors*! 
Our "passive" house isn't as cheap to run as you're led to believe. "A" rated, my sharmy arse!
Blower test and calcs all prove that it's "A", but it's more expensive to run than the "G" rated house we lived in before.
(*I'm informed bi-folds don't meet "A" rating requirements, or didn't when we were building.)
Our "passive" house isn't as cheap to run as you're led to believe. "A" rated, my sharmy arse!
Blower test and calcs all prove that it's "A", but it's more expensive to run than the "G" rated house we lived in before.
(*I'm informed bi-folds don't meet "A" rating requirements, or didn't when we were building.)
RC1807 said:
Our "passive" house isn't as cheap to run as you're led to believe. "A" rated, my sharmy arse!
Blower test and calcs all prove that it's "A", but it's more expensive to run than the "G" rated house we lived in before.
Really? How is that even possible?! Blower test and calcs all prove that it's "A", but it's more expensive to run than the "G" rated house we lived in before.
What do you put it down to - heating system? What do you have?
I have no experience with passive house developments however I am pretty knowledgeable regarding the code for sustainable homes as I was a licensed assessor up until this year.
My personal experience is that dwellings aiming to achieve high levels of certification inevitably end up using electricity as the primary heating and hot water source via MVHR and some form of heat pump. These systems in my experience never get anywhere near the claimed efficiency/running costs.
On one development I certified the developer had to pay off the residents as the exhaust air heat recovery pump used was consuming 3x's the projected electricity consumption meaning a new 2 bed house was costing around £1600 in energy costs (my 100 year old 4 bed is around £1200)
My personal experience is that dwellings aiming to achieve high levels of certification inevitably end up using electricity as the primary heating and hot water source via MVHR and some form of heat pump. These systems in my experience never get anywhere near the claimed efficiency/running costs.
On one development I certified the developer had to pay off the residents as the exhaust air heat recovery pump used was consuming 3x's the projected electricity consumption meaning a new 2 bed house was costing around £1600 in energy costs (my 100 year old 4 bed is around £1200)
barryrs said:
I have no experience with passive house developments however I am pretty knowledgeable regarding the code for sustainable homes as I was a licensed assessor up until this year.
My personal experience is that dwellings aiming to achieve high levels of certification inevitably end up using electricity as the primary heating and hot water source via MVHR and some form of heat pump. These systems in my experience never get anywhere near the claimed efficiency/running costs.
On one development I certified the developer had to pay off the residents as the exhaust air heat recovery pump used was consuming 3x's the projected electricity consumption meaning a new 2 bed house was costing around £1600 in energy costs (my 100 year old 4 bed is around £1200)
Why am I not surprised? Theory and practice, just like so many Green ideas...My personal experience is that dwellings aiming to achieve high levels of certification inevitably end up using electricity as the primary heating and hot water source via MVHR and some form of heat pump. These systems in my experience never get anywhere near the claimed efficiency/running costs.
On one development I certified the developer had to pay off the residents as the exhaust air heat recovery pump used was consuming 3x's the projected electricity consumption meaning a new 2 bed house was costing around £1600 in energy costs (my 100 year old 4 bed is around £1200)
I was part of a team that built at the time two of the largest non domestic PH certified buildings in the UK. This was before it became slightly more mainstream, so we struggled for certified products to install.
We struggled to achieve the primary energy demand, and new IT equipment had to be purchased to ensure we fell under the threshold. We had to consider anything that used power so everything was reviewed and recorded and a table produced to show usage, expected hours of use etc.
I think the introduction of Led lighting, and new improved rated appliances certainly helps with the target due to the much reduced energy consumption. It will also be dependent on your usage, i/e if you work at home, have a large number of people in the house, kids that use the toaster five times a day etc.
If it was my money, I would certainly take advantage of the PHPP software and the PH principles, but I wouldn't go for full certification. Especially not if restricts some key aspects you would like to introduce to the house (Bi-folds, being one example - although I do believe there is a certified option now)
I would concentrate on air tightness and getting the mech vent correct, along with high levels of insulation to provide a year round comfortable environment. Remember insulation keeps heat out as well as in.
If you need any contacts in the PH world, more than happy to help. I can also recommend a good architect who has done a few residential developments.
We struggled to achieve the primary energy demand, and new IT equipment had to be purchased to ensure we fell under the threshold. We had to consider anything that used power so everything was reviewed and recorded and a table produced to show usage, expected hours of use etc.
I think the introduction of Led lighting, and new improved rated appliances certainly helps with the target due to the much reduced energy consumption. It will also be dependent on your usage, i/e if you work at home, have a large number of people in the house, kids that use the toaster five times a day etc.
If it was my money, I would certainly take advantage of the PHPP software and the PH principles, but I wouldn't go for full certification. Especially not if restricts some key aspects you would like to introduce to the house (Bi-folds, being one example - although I do believe there is a certified option now)
I would concentrate on air tightness and getting the mech vent correct, along with high levels of insulation to provide a year round comfortable environment. Remember insulation keeps heat out as well as in.
If you need any contacts in the PH world, more than happy to help. I can also recommend a good architect who has done a few residential developments.
Rosscow said:
RC1807 said:
Our "passive" house isn't as cheap to run as you're led to believe. "A" rated, my sharmy arse!
Blower test and calcs all prove that it's "A", but it's more expensive to run than the "G" rated house we lived in before.
Really? How is that even possible?! Blower test and calcs all prove that it's "A", but it's more expensive to run than the "G" rated house we lived in before.
What do you put it down to - heating system? What do you have?
After 1 year in the house, paying an estimated bill every 2 months, I had a massive debt to repay then over the following year, which was scary. (My build thread's noted in the Wiki - I used to be "5PotTurbo")
We're now in the habit of only using UFH when it's really cold, and not using the air circulation (in/out) in the Summer, but only for air extraction due to steam from shower rooms. Windows are open in the summer for circulation.
barryrs said:
I have no experience with passive house developments however I am pretty knowledgeable regarding the code for sustainable homes as I was a licensed assessor up until this year.
My personal experience is that dwellings aiming to achieve high levels of certification inevitably end up using electricity as the primary heating and hot water source via MVHR and some form of heat pump. These systems in my experience never get anywhere near the claimed efficiency/running costs.
On one development I certified the developer had to pay off the residents as the exhaust air heat recovery pump used was consuming 3x's the projected electricity consumption meaning a new 2 bed house was costing around £1600 in energy costs (my 100 year old 4 bed is around £1200)
Very interesting view. What do you consider the most efficient (or cheapest!) primary heating/hot water source is?My personal experience is that dwellings aiming to achieve high levels of certification inevitably end up using electricity as the primary heating and hot water source via MVHR and some form of heat pump. These systems in my experience never get anywhere near the claimed efficiency/running costs.
On one development I certified the developer had to pay off the residents as the exhaust air heat recovery pump used was consuming 3x's the projected electricity consumption meaning a new 2 bed house was costing around £1600 in energy costs (my 100 year old 4 bed is around £1200)
barryrs said:
My personal experience is that dwellings aiming to achieve high levels of certification inevitably end up using electricity as the primary heating and hot water source via MVHR and some form of heat pump. These systems in my experience never get anywhere near the claimed efficiency/running costs.
....the projected electricity consumption meaning a new 2 bed house was costing around £1600 in energy costs (my 100 year old 4 bed is around £1200)
My experience exactly. "A" rating looks great, on paper. Reality is very different.....the projected electricity consumption meaning a new 2 bed house was costing around £1600 in energy costs (my 100 year old 4 bed is around £1200)
"B" is probably the best you'd want to go for on payback basis.
The Moose said:
Very interesting view. What do you consider the most efficient (or cheapest!) primary heating/hot water source is?
Number one is fabric first and air tightness as mentioned above so that you minimise your energy consumption from the start rather than offset it with renewables. That approach with a natural gas heating & hot water system with renewable/low carbon add-ons is my preferred approach.I have the ridiculous situation with one LA that stipulates that any new dwellings must produce 10% of energy consumption (measured in kw per m2 per year) using renewables when i can simply reduce the consumption by a greater amount by upgrading the fabric over building regs. The result is we are producing houses that simply comply with building regs and offsetting consumption by chucking a pathetic 2kw pv system on the roof.
RC1807 said:
Rosscow said:
RC1807 said:
Our "passive" house isn't as cheap to run as you're led to believe. "A" rated, my sharmy arse!
Blower test and calcs all prove that it's "A", but it's more expensive to run than the "G" rated house we lived in before.
Really? How is that even possible?! Blower test and calcs all prove that it's "A", but it's more expensive to run than the "G" rated house we lived in before.
What do you put it down to - heating system? What do you have?
After 1 year in the house, paying an estimated bill every 2 months, I had a massive debt to repay then over the following year, which was scary. (My build thread's noted in the Wiki - I used to be "5PotTurbo")
We're now in the habit of only using UFH when it's really cold, and not using the air circulation (in/out) in the Summer, but only for air extraction due to steam from shower rooms. Windows are open in the summer for circulation.
Would you say it's the air source heat pump that is the problem?
Equus said:
Such a condition under Planning can now be easily challenged and removed.
Not according to the 2015 adopted local plan unfortunately.The only way this can be challenged at the moment is if meeting this condition adds more than 5% to the build costs excluding things such as site remediation and landscaping.
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