Part L and DEAP relationship

sydthebeat

Ive just completed a DEAP analysis on a house thats passive level (on its way to being certified).
As you can imagine all elements are seriously good.

The dwelling will have a manual feed wood stove feeding into a 1000 litre stratification thermal store. It will also have 90 evacuated tubes feeding this store as well. The UFH will then be pulled from this store by time / temp controls.

Ive a CPC of 0.299 and a EPC of 0.299

Now the part i dont get.....

Total solar contribution = 3690 yet.......... Part L contribution = 7.95
wood as main space heating = -197 ........ Part L contribution = -0.32
wood as main DHW system = 1167 .......... Part L contribution = 2.51

total thermal equivalent = 4708 ............. Part L contribution = 10.14

(yes i know theres minus figures there perhaps someone can clarify... )

but essentially, a passive house with solar and wood heating just barely meets the renewable requirement??? WTF


This just goes to show that the renewable requirement being a function of the floor area versus assessed energy needs is obscure and penal. It should so obviously be a function of a percentage of the energy requirement as assessed.

BryanF

A building shall be designed and constructed so as to ensure that the energy performance of the building is such as to limit the amount of energy required for the operation of the building and the amount of carbon dioxide (CO2) emissions associated with this energy use insofar as is reasonably practicable.....

L3 For new dwellings, the requirements of L1 shall be met by: -
(a) providing that the energy performance of the dwelling is such as to limit the calculated primary energy consumption and related carbon dioxide (CO2) emissions insofar as is reasonably practicable, when both energy consumption and carbon dioxide (CO2) emissions are calculated using the Dwelling Energy Assessment Procedure (DEAP) published by Sustainable Energy Authority of Ireland;

(b) providing that, for new dwellings, a reasonable proportion of the energy consumption to meet the energy performance of a dwelling is provided by renewable energy sources;

plenty of letters to building control looking for dispensations on the way...

sydthebeat

BryanF wrote: »

A building shall be designed and constructed so as to ensure that the energy performance of the building is such as to limit the amount of energy required for the operation of the building and the amount of carbon dioxide (CO2) emissions associated with this energy use insofar as is reasonably practicable.....

L3 For new dwellings, the requirements of L1 shall be met by: -
(a) providing that the energy performance of the dwelling is such as to limit the calculated primary energy consumption and related carbon dioxide (CO2) emissions insofar as is reasonably practicable, when both energy consumption and carbon dioxide (CO2) emissions are calculated using the Dwelling Energy Assessment Procedure (DEAP) published by Sustainable Energy Authority of Ireland;

(b) providing that, for new dwellings, a reasonable proportion of the energy consumption to meet the energy performance of a dwelling is provided by renewable energy sources;

plenty of letters to building control looking for dispensations on the way...

As the regs are so prescriptive I don't think local building control officers would accept dispensations. Its one aspect where I don't think 'opinion' washes.

sinnerboy

461m2 ? Big house syd.

Somethings wrong with the wood space heating. Is there an error in the entry for % efficiency of the boiler ?

creedp

sydthebeat wrote: »

As the regs are so prescriptive I don't think local building control officers would accept dispensations. Its one aspect where I don't think 'opinion' washes.

This is an issue which I had to grapple with as well and it came down to a choice between using default u values for fabric/windows in order to reduce the efficiency of the house thereby increase the SH demand for HP or incurring unplanned expenditure in installing SH panels in order to achieve the magical 10. In my opinion this dichotomy between the BER process and Part L seriously discredits the BER process as I can see why the Regs would be designed to increase efficiency but when they can encourage people to be less efficient there is something really wrong!

sydthebeat

yeah SB, the attic is within the insulation envelope and has a fixed stair access, so that puts the floor area up another 153 sq m.
Without this extra 153 sq m the part l contribution is still only 14.77

I cannot figure out what the issue is with the main space heating:

Wood stove 80% efficient
the control and responsive inputs are:
central heating systems - solid fuel boilers - manual feed independent boiler in heated space - both rads and UFH in conc slab, living area by UFH - time / temp zone control... plus integrated thermal store present.

I cant find what the issue is.

I think the contribution algorithims in DEAP need to be looked at again to reflect the low energy direction our building regulations are going in.
This dwelling will most probably be heated, space and DHW, by solar alone from april to sept... so the solar contribution is grossly undervalued.

MicktheMan

sydthebeat wrote: »

(on its way to being certified).

The dwelling will have a manual feed wood stove feeding into a 1000 litre stratification thermal store.

The UFH will then be pulled from this store by time / temp controls.

Hi Syd,
I don't want to derail the thread but, assuming the house gets certified, is the ufh not overkill? Would it not have been better to distribute the majority of stored heat via the mvhr rather than go to the expense of a seperate wet distribution system for a house of that size?

creedp

MicktheMan wrote: »

Hi Syd,
I don't want to derail the thread but, assuming the house gets certified, is the ufh not overkill? Would it not have been better to distribute the majority of stored heat via the mvhr rather than go to the expense of a seperate wet distribution system for a house of that size?

I suppose if you have the resources to build that size of house to a passive std the incremental cost of installing UFH wouldn't be a deal breaker. Theother point is that although people opt for this std of build in the knowledge of its low space heating requirements, its a comforting thought to have the UFH in place in case ...

sydthebeat

MicktheMan wrote: »

Hi Syd,
I don't want to derail the thread but, assuming the house gets certified, is the ufh not overkill? Would it not have been better to distribute the majority of stored heat via the mvhr rather than go to the expense of a seperate wet distribution system for a house of that size?

yeah, i dont want to get into too much of the specifics as goes against the theme of the thread, but the UFH was a choice of the client. You probably know who it is as he posts here quite often and regularly in the 'live self builds' thread. The installation of the UFH is was borne from a fear that the house wouldnt perform continuous over time as theorised. The UFH adds an element of reserve heating system installation.

to be honest, i not even sure how that system would be inputted into DEAP

sas

sydthebeat wrote: »

You probably know who it is as he posts here quite often and regularly in the 'live self builds' thread. The installation of the UFH is was borne from a fear that the house wouldnt perform continuous over time as theorised. The UFH adds an element of reserve heating system installation.

Hey, it's my house.

In the depths of winter I fully believe I'll need the UFH. The MHRV heating approach tends to struggle to lift the temp in masonry houses I'm told. You just can't deliver enough heat with it apparently. We've got the facility to do this too so I'll see how it works.

Also, if my job disappeared underneath me in the morning and I was unable to pay my mortgage, I'd be trying to sell a great big house with no heating system which is how the majority of potential purchasers would see it. A PH cert means very little to 99.9% of the population. Now I have a heat distribution system for downstairs (UFH) and have made provision to add rads upstairs later if needs be.

Relatively cheap insurance policy in my opinion.
If it turns out I never use it then I can live with the additional spend.

Do-more

sas wrote: »

Hey, it's my house.

In the depths of winter I fully believe I'll need the UFH. The MHRV heating approach tends to struggle to lift the temp in masonry houses I'm told. You just can't deliver enough heat with it apparently. We've got the facility to do this too so I'll see how it works.

Also, if my job disappeared underneath me in the morning and I was unable to pay my mortgage, I'd be trying to sell a great big house with no heating system which is how the majority of potential purchasers would see it. A PH cert means very little to 99.9% of the population. Now I have a heat distribution system for downstairs (UFH) and have made provision to add rads upstairs later if needs be.

Relatively cheap insurance policy in my opinion.
If it turns out I never use it then I can live with the additional spend.

I've come around to the same thinking myself, everyone has told me I would never be able to sell a modern house here if it didn't have underfloor heating if we ever came to situation that we had to sell.

I also looked at heating the house via duct heaters in the ventilation but it's a non runner because of the low heat capacity of air.

I've just had the heat losses for all the individual rooms calculated on the basis of worst case ambient temperature and allowing for no passive or solar gains so as to size the UFH loops for each room.

It is a little alarming that the sum of all those losses is approx. 13kW when PHPP calculates the max. demand at less than 3kW.

Whilst I don't expect the extreme of this worst case scenario to ever arise I do think it is sensible to not rely on PHPP for sizing the heating system.

My primary heat source will be 6kW and I will have back ups in place which can supply up to 16kW in total.

[on topic] I do think that Part L needs to be urgently reviewed with the advent of very low energy demands being the norm.

I haven't got my head around the building regs here in Sweden but it's based on energy efficiency in relation to the electrical consumption of the house with the ability to offset with solar thermal and solar PV.

If anyone wants to try and figure them out with the help of Google translate and a scientific calculator you can read them here (pdf).

fclauson

So I have done A LOT of work on DEAP and Part L spreadsheets etc etc

Renewables compliance is a menace if you cannot get a dispensation from the rigours of TGD. The word reasonable in the Planning Act actually means "spend money on lawyers"

So back to compliance - DEAP is seriously flawed - as the insulation levels go up - your ability explicitly to comply with renewables becomes hard because the heat demand for the build drops.
HP become untenable as the DEAP SPF for hotwater calc kills them and if you space heat demand then their contribution is very low if not at all. (and these are supposed to be the future - either DEAP is flawed or HPs are)

You calcs - have you included in your renewable the contribution that the thermal store brings to space heating - using http://www.seai.ie/Your_Building/BER/BER_FAQ/FAQ_DEAP/DEAP_Appendix_Q_Specific_Features/Solar_Space_Heating_Individual_Heating_Systems_.html

On the UFH in a Passive house - you have to remember a Passive House has a demand - all be it low. Mine for example needs 3.5Kw all the time every day when then temp is at -1. If I do not put in 3.5 Kw then then house temp will fall and I will need to put in 4,5,6,7,8,..20 to bring it back to temp (block built - so massive thermal resitance to movement) . And that demand is based on a whole bunch of assumptions about body heat, light heat etc etc - People living in a house upset the passiveness of it.

sydthebeat

thanks fclauson, i hadn't actually included solar in the renewable technology section.... i hadnt come up against this before. thanks for that, i actualy had a chat with beyonepassive this evening who also turned me onto it.

Ill augment the calcs on monday to see what change there is. The second floor area will be removed from further calculations as theres a doubt over the continuous existence of a fixed stair access here. That will immediately help.

Ill post again on monday...

any idea about why my main space heating system is outputting a negative thermal equivalent??

fclauson

sydthebeat wrote: »

any idea about why my main space heating system is outputting a negative thermal equivalent??

Thats because your solar and other heat gains exceeds the demand to keep the house warm (i.e in DEAP terms your house is thermal energy positive)

As we all know this is nonsense - there will always be times when you have to add heat to the house - DEAP just cannot understand this.

There is also assumptions in DEAP of the "mean internal temp" which is an average of your "living space" which is kept at one temp and the rest of the house is kept at another.

For my build this comes in at 18.03 which is not the 20 degrees that PHPP aspires to

So DEAP and PHPP are missalinged in their maths to determine demand

Do-more

fclauson wrote: »

HP become untenable as the DEAP SPF for hotwater calc kills them and if you space heat demand then their contribution is very low if not at all. (and these are supposed to be the future - either DEAP is flawed or HPs are)

I think it is probably a bit of both.

Having done lots of research on heat pumps at this stage, the argument for their use becomes less and less as the heat demand falls.

If you take the example of a passive house where the space heating demand is 3000kWhr/a or less (200m2 house @ 15kWhr/m2/a) the circulation pumps for a GSHP are likely to consume about 750kWhr so even if you have a high COP for the heat pump if you look at the COP of the system as a whole it will be considerably less due to the power consumption of the pumps.

And of course the COP gets even worse if you are producing DHW with the heat pump as the COP declines the larger delta T becomes.

You need to look at it on a case by case basis and work out the figures for the whole system, but I would think that in Ireland there are probably very few situations where a heat pump is the best solution for heating a passive house.

Personally speaking if I had mains gas available that's what I would go for in a heartbeat.

sinnerboy

fclauson wrote: »

Thats because your solar and other heat gains exceeds the demand to keep the house warm (i.e in DEAP terms your house is thermal energy positive)

So DEAP and PHPP are missalinged in their maths to determine demand

Agreed. As an energy modelling tool PHPP is far more reliable.
DEAP ( primary purpose is to produce BER certs and demonstrate (aspects of ) Part L compliance ) ..... has limitations. Ahem!

No6

sinnerboy wrote: »

Agreed. As an energy modelling tool PHPP is far more reliable.
DEAP ( primary purpose is to produce BER certs and demonstrate (aspects of ) Part L compliance ) ..... has limitations. Ahem!

Its a bit quicker though!!!:D

Do-more

Do-more wrote: »

I've just had the heat losses for all the individual rooms calculated on the basis of worst case ambient temperature and allowing for no passive or solar gains so as to size the UFH loops for each room.

It is a little alarming that the sum of all those losses is approx. 13kW when PHPP calculates the max. demand at less than 3kW.

Scratch all that!



I must learn to read excel spreadsheets a bit better! But my excuse is the descriptions were all in Swedish.

I managed to tot up what were already the cumulative totals of the heat losses to arrive at the 13kW.

In fact the worst case scenario of heat losses at -10 degrees ambient with no allowance for passive or solar gains totals to 3,332W when PHPP gives the heating load as 2,637W

Hopefully I am interpreting these figures correctly now.

fclauson

DEAP and PHPP actually have the same backbone - IS EN 13790 - if you pick through the spread sheet version of DEAP and PHPP you will see that the underlying figures are not wholly dissimilar - so you can get some good build performance data from a DEAP spreadsheet - if I had the time I would build a simple IS EN 13790 model which would wholly simplify the basic heat loss calculation you need to do on a house to determine its performance.

Where the divergence arises is that DEAP then uses these numbers to make some assumptions on overall demand which is different from PHPP

reference for IS EN 13790 http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=41974_

therightangle

sydthebeat wrote: »

As the regs are so prescriptive I don't think local building control officers would accept dispensations. Its one aspect where I don't think 'opinion' washes.

Opinion can be backed up by calcs to demonstrate the excessive proportion of renewable contribution to non-renewable contribution. This has been accepted by a BCO recently for a passive house - the precedent is there.

sydthebeat

therightangle wrote: »

Opinion can be backed up by calcs to demonstrate the excessive proportion of renewable contribution to non-renewable contribution. This has been accepted by a BCO recently for a passive house - the precedent is there.

'certified' passive house????

fclauson

Syd
try "loosing" you MHRV certification and enter default values as allowed for in DEAP
Similarlly try just using 0.08 for you PSI thermal bridge rather than anything more fancy - assuming you build to ACDs
Finally "loose" you window certs and enter the defaults permitted for your window type

Also you might want to down grade you airtightness to a worse figure

now do you comply :D

I would be interested ?

creedp

fclauson wrote: »

Syd
try "loosing" you MHRV certification and enter default values as allowed for in DEAP
Similarlly try just using 0.08 for you PSI thermal bridge rather than anything more fancy - assuming you build to ACDs
Finally "loose" you window certs and enter the defaults permitted for your window type

Also you might want to down grade you airtightness to a worse figure

now do you comply :D

I would be interested ?

Now you're speaking my language .. To qualify under Part L with a HP I used the certified figures for MHRV but used 0.15 for PSI thermal bridge (terrible build stds!); forgot to seal an opening to attic during airtightness test and used default values for windows in order to get in marginally above 10. Its all been a very big eye opener for me but rightly or wrongly sometimes you have to do what has to be done ... I will install SP for DHW in a couple of years once (if ever) financial pressures subside and then I will he happy in the knowledge that all is well with DEAP.

fclauson

creedp wrote: »

Now you're speaking my language .. To qualify under Part L with a HP I used the certified figures for MHRV but used 0.15 for PSI thermal bridge (terrible build stds!); forgot to seal an opening to attic during airtightness test and used default values for windows in order to get in marginally above 10. Its all been a very big eye opener for me but rightly or wrongly sometimes you have to do what has to be done ... I will install SP for DHW in a couple of years once (if ever) financial pressures subside and then I will he happy in the knowledge that all is well with DEAP.

The ROI on SPs are not great - say they costs 5K to install 6sqM which gives about 2600Kwh/Annum

Assume you are using a HP with an SPF of 2.5 to heat water (which is low for a good heat pump) - and you are getting your electricity @ Kwh @ 16c - so 16c /2.54 = 6.3c per kwh of hot water

then work on an energy inflation rate of say 8% (that is what my magic crystal ball says prices will go up by)

after 15 years you would have paid just under €3K for your electricity for the hot water from your HP your SPs would have produced.

So if the SPs costs 5K and after 15 years you would have paid 3K for your electricity to run you HP - do SPs make sense - and I have not factored in the electricity the solar panels use to run the pumps etc.

Is my maths right ?

PS - sorry for going off thread - but I thought the above maths might be of interest

sydthebeat

fclauson wrote: »

Syd
try "loosing" you MHRV certification and enter default values as allowed for in DEAP
Similarlly try just using 0.08 for you PSI thermal bridge rather than anything more fancy - assuming you build to ACDs
Finally "loose" you window certs and enter the defaults permitted for your window type

Also you might want to down grade you airtightness to a worse figure

now do you comply :D

I would be interested ?

Before i do this i want to clarify my first post.
Ive made three main alterations to the assessment so far
1. removed the third floor as fixed access wont be incorporated
2. assessed using DEAP 3.2
3. included solar contribution to space heating

these changes have brought the renewable requirement to 16.89 (up from 10.14)

Ill do what you are suggesting above, and i know it will give greater renewable requirement.... im not sure that i agree in this case as the requirement is met. But i see what you are trying to show.
its clear that linking renewable requirement to a 'per sq m' basis rather than an energy demand basis is seriously flawed.

sydthebeat

ok made those alterations.

default MHRV and 0.08 thermal bridging

renewables = 21.64
rating still = A2
energy value up 10kw/m2/yr to = 44.39

frustrating !!!!!!

even more infuriating, thermal bridging at 0.15 offers renewables of 26.98 !!!! :mad:

sydthebeat

fclauson wrote: »

now do you comply :D

non compliance wasnt an issue, but the low renewable offering was very surprising.

I cannot see how houses will comply under Part L 2011 without some of these 'creative accounting' measures as suggested above.
I think we need to come together here and put a mass warning to DOEHLG

fclauson

sydthebeat wrote: »

... thermal bridging at 0.15 offers renewables of 26.98 !!!! :mad:

Thought so - its sort of counter intuative - you reach a point where investing less gives you better compliance

Obviously this is a serious quirk which needs investigating – we have a situation that to meet Part L requirements I either have to Down grade to inferior worse performing products and down grading the overall energy efficiency of my build or Invest more money to generate renewables to meet the Part L requirement (the mix of which has to be closely scrutinised to ensure I am generating renewable which can actually be used e.g. increasing the Solar Thermal square meters deployed would allow me to comply but put me in a position where I have an excess of solar heat for much of the summer

creedp

fclauson wrote: »

The ROI on SPs are not great - say they costs 5K to install 6sqM which gives about 2600Kwh/Annum

Assume you are using a HP with an SPF of 2.5 to heat water (which is low for a good heat pump) - and you are getting your electricity @ Kwh @ 16c - so 16c /2.54 = 6.3c per kwh of hot water

then work on an energy inflation rate of say 8% (that is what my magic crystal ball says prices will go up by)

after 15 years you would have paid just under €3K for your electricity for the hot water from your HP your SPs would have produced.

So if the SPs costs 5K and after 15 years you would have paid 3K for your electricity to run you HP - do SPs make sense - and I have not factored in the electricity the solar panels use to run the pumps etc.

Is my maths right ?

PS - sorry for going off thread - but I thought the above maths might be of interest

I agree ROI on SP aren't great and that is why I wasn't going to install them initally (I won't pretend to validate your calcs by the way!). However, leaving ROI aside for a moment I would like to think that using 'free' energy is something that should be encouraged and in addition it gives you less of a crisis of conscience when your running showers/baths or giving the car a warm wash! In additon, the difficulty with HP and DHW is that temp is limited to 50c which means it has to be boosted by immersion and I have an aversion to immersion. Having said that I won't be installing SP's for a little bit as I am very much licking my financial wounds at present and basically focussing on the short rather than longer term.

creedp

fclauson wrote: »

Thought so - its sort of counter intuative - you reach a point where investing less gives you better compliance

Obviously this is a serious quirk which needs investigating – we have a situation that to meet Part L requirements I either have to Down grade to inferior worse performing products and down grading the overall energy efficiency of my build or Invest more money to generate renewables to meet the Part L requirement (the mix of which has to be closely scrutinised to ensure I am generating renewable which can actually be used e.g. increasing the Solar Thermal square meters deployed would allow me to comply but put me in a position where I have an excess of solar heat for much of the summer

Really though the issue is one of an holistic approach to design and build methods. It probably makes sense if you design and build from the start using the DEAP approach. The day has well and truly passed when you get your planning and builder and decide as you go along how the whole thing will pull together .. its a science now and an ever evolving one at that. 3 years ago I was talking to guys who thought a 150mm cavity was madness. Even on here a year ago 200mm to 225mm was seen to be the de riguer in cavity size, whereas now it seems that unless you go 300mm you're in dinosaur territory .. where will it end. At the end of the day you have to start somewhere and then you have the rest of your days to kick yourself in the backside when you see how it could have been done differently/better .. such is life!

fclauson

creedp wrote: »

....that unless you go 300mm you're in dinosaur territory .. ...

Whopps - I am at 250mm - but I am short and fat (bungalow) so view that most of the heat will go up (500mm insulaiton) or down (200mm insulation ) so the sides can be slightly Comprimised (still at 0.13 U its not bad)

creedp

fclauson wrote: »

Whopps - I am at 250mm - but I am short and fat (bungalow) so view that most of the heat will go up (500mm insulaiton) or down (200mm insulation ) so the sides can be slightly Comprimised (still at 0.13 U its not bad)

That's the point though .. a couple of years ago 250mm would have been almost unheard of (in my circle of friends in any case!) whereas now 300mm is seemingly where things are! Maybe we'll be heading to 400mm next .. there is abviously a point where the ROI doesn't make sense wherever that is.

sydthebeat

theres a buildability issue creeping in here too.

lads, can we keep this to just Part L and DEAP

andif you want to open another thread on future build methods etc i can move posts.

therightangle

Originally Posted by therightangle :
Opinion can be backed up by calcs to demonstrate the excessive proportion of renewable contribution to non-renewable contribution. This has been accepted by a BCO recently for a passive house - the precedent is there.

sydthebeat wrote: »

'certified' passive house????

Yes it was a certified passive house.

therightangle

fclauson wrote: »

Thought so - its sort of counter intuative - you reach a point where investing less gives you better compliance

Obviously this is a serious quirk which needs investigating – we have a situation that to meet Part L requirements I either have to Down grade to inferior worse performing products and down grading the overall energy efficiency of my build or Invest more money to generate renewables to meet the Part L requirement (the mix of which has to be closely scrutinised to ensure I am generating renewable which can actually be used e.g. increasing the Solar Thermal square meters deployed would allow me to comply but put me in a position where I have an excess of solar heat for much of the summer

Maybe this will be a worthwhile exercise in how to reach the renewables target whilst:
a) maintaining BER rating
b) ditching the more expensive features

For instance, I have tried moving South ,East ,West windows to double instead of triple which worked to reach the renewables target, and saved a considerable amount of money, without affecting the rating, as the greater solar transmittance made up for the poorer u-value. (Though at 46% glazing overall, the u-value still had to be good!)

This is where having the WEP list of windows can be handy, so that you can try a range of products to find the right balance.

sydthebeat

therightangle wrote: »

Yes it was a certified passive house.

thats exactly my point....

a certified passive house will have documented evidence of performance.
So its much easier for the BCO to accept a derivation from the regs when offered this evidence.

A lot of people are using the phpp as a design tool and creating "low energy" home which may be passive by calculation, yet are not going down the certified route for whatever reason. I would imagine its much much harder for a BCO to accept a derivation from the regs when not offered a certification

fclauson

therightangle wrote: »

Maybe this will be a worthwhile exercise in how to reach the renewables target whilst:
a) maintaining BER rating
b) ditching the more expensive features

For instance, I have tried moving South ,East ,West windows to double instead of triple which worked to reach the renewables target, and saved a considerable amount of money, without affecting the rating, as the greater solar transmittance made up for the poorer u-value. (Though at 46% glazing overall, the u-value still had to be good!)

This is where having the WEP list of windows can be handy, so that you can try a range of products to find the right balance.

I think you miss the point here - DEAP is flawed - down grading the thermal properties of components may reach compliance but reduces the thermal efficiency of you build

Thermal transmittance does not compensate for U-value - having high solar gain during the day does not make up equally for thermal loss at night - its much more complicated than that - there is also the challenge of thermal comfort (double glaze glass is cold to the touch or to be near - triple is not)

therightangle

fclauson wrote: »

I think you miss the point here - DEAP is flawed - down grading the thermal properties of components may reach compliance but reduces the thermal efficiency of you build

Thermal transmittance does not compensate for U-value - having high solar gain during the day does not make up equally for thermal loss at night - its much more complicated than that - there is also the challenge of thermal comfort (double glaze glass is cold to the touch or to be near - triple is not)

Im well aware it reduces the efficiency of the build.

But in the meantime, I have built a compliant dwelling for several thousand less by working within the DEAP rules we have.

I sincerely wish the best of luck to anyone that highlights the flaws of DEAP and pushes to get it improved, but I cant wait around for that.

fclauson

I received the following advice on Friday

Read part L - specifically 0.1.2.1

If I understand this correctly the primary concern of Part L is to achieve a drop in CO2 output.
to quote
Meeting the performance levels specified for items (b) to (i) will not necessarily mean that the level specified for primary energy consumption and related CO2 emissions [item (a)] will be met.

So if you achieve the 0.1.2.1 (a) i.e. the reduction in MPEC and CPC to below the required standard - then you could (and should and I will) argue that you are complient with L1
A building shall be designed and constructed so as to ensure that the energy performance of the building is such as to limit the amount of energy required for the operation of the building and the amount of carbon dioxide (CO2) emissions associated with this energy use insofar as is reasonably practicable.

In actual fact lowering your building elements values to be complient with the renewables requirment 1.2.1 could and should be argued is failing to comply with L1 - remember the 10kwh/m2 is GUIDENCE and not the planning act itself.

So if you want to use the better quality items then I suggest you discuss with you local building control officer for an exeption to using DEAP as the method of compliance - and raise the point above that you wish to comply with L1 but you are being defeted by the TGD section 1.2.1 wich is trying to make you downgrade you building and thus make it create more CO2

Thougths anybody ????