Over the past year or so, the majority of the insulation queries I have received concern the changes to NZBC H1 and how to use the Calculation Method.
So I thought my first Detailed post should be a worked example of the Calculation Method in action. When should you use the Calculation Method?
The Calculation Method is particularly useful if:
- Glazing is above 30% of the total wall area — but less than 40%
- You have mixed wall claddings
- Design requires reduction of construction R-values in one area, and to meet compliance you need to increase the R-value in another area.
The example is of a house in Climate zone 1, with a large north facing window. The designer in this example has been asked to reduce the cost of this window and one of the options is for the window to be single glazed and the level of insulation increased.
In the example I have used the BRANZ Calculation Spreadsheet and the BRANZ House Insulation Guide to work out the construction R-value of the various building elements.
June 8, 2010 at 11:23 am
HI,
I was wondering if the calculation method needs to be done all the time, due to the ceiling insulation?
The ceiling insulation around the perimeter of the walls where it meets the roof, the roofing paper has to be at least 25mm from the insulation material, this reduces the thickness of insulation needed, the recommended insulation value sometimes cannot fit in this gap, so a lesser value has to be installed.
This is usally the case with a roof pitch around 30 deg or less, depending on the rafter/truss size.
We sometimes use masonry batts as they are not so thick.
This is also an issue with skillion roofs.
So if the window area is less than 30% does a calculation method still need to be done?
Thanks
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Bhavna Prentice:
June 8th, 2010 at 12:54 pm
Hi Daniel,
You are correct, if the house has been designed and the roof cannot accommodate the insulation around the perimeter, the Calculation method is ideal. Our technical update on this may be of some assistance and can be downloaded here – http://www.pinkbatts.co.nz/assets/Uploads/PDFS/Technical-UpdateRoof-Underlay-and-Insulation-Clearances.pdf
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June 8, 2010 at 11:25 am
I am currently detailing renovations to an existing house with a skillion roof and no roof insulation. The roof construction is exposed 90 x 45mm rafters and collar ties with particleboard ceiling lining above, tile battens and Hardies shingle roof. The roof and tile battens are to be removed and replaced with a longrun metal roof over 90 x 45mm purlins on edge @1200mm crs. I am proposing to insulate the roof by fitting R2.0 batts between the rafters and a new Gib ceiling to the underside of rafters & collar ties. Then fiot R1.39 Polystyrene sheets above the particle board between purlins.
I believe the sum of this insulation is the best I can achieve without rebuilding this roof from scratch.
Am I going to be able to use the sum of this insulation in the calculation method?
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Bhavna Prentice:
June 8th, 2010 at 12:55 pm
Hi Greg,
You can use the construction R-value for your system in the Calculation method; this is slightly different to the sum as it will take into account the thermal bridging effect of the timber. Unfortunately the BRANZ House insulation guide has not worked out the construction R-value for the roof system you propose. My first step would be to work out the construction R-value using ‘NZS4214:2006 Methods of determining the total thermal resistance of parts of buildings’. You can then use this construction R-value in the Schedule or Calculation Method.
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June 8, 2010 at 11:36 am
I see on your post that you have typical “construction R values”… I can’t find this on the Pink Batts website, where can I find a full lidsting of these?
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Bhavna Prentice:
June 8th, 2010 at 12:56 pm
Hi Ralf,
We have a summarised version on page 7 and 8 of our Pink® Batts® NZBC H1 Energy Efficiency Guide (http://www.pinkbatts.co.nz/assets/Uploads/PDFS/Pink-Batts-NZBC-H1-Energy-Efficiency-Guide.pdf). The full version is available through BRANZ, in the form of the BRANZ House Insulation Guide.
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June 8, 2010 at 11:37 am
HI,
My current project is a renovation, there are some extensions and some renovations and alterations to the existing structure, Does the H1 calculation still need to be done for the whole dwelling or just the new additions?
If so, the is the addition treated as a separate building?
Thanks
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Bhavna Prentice:
June 8th, 2010 at 12:58 pm
Hi,
NZS 4218:2009 Thermal Insulation – Housing and Small Buildings Appendix D – Alterations is an informative section with some comments on how to approach alterations. This section states that compliance methods can be applied to either the whole building or the alteration only. And in either case only the building elements in the alteration are required to meet the construction R-values.
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June 8, 2010 at 11:45 am
When calculating insulation requierments to NZS4218:2004 you only need to insulate around the “building envelope”. You can choose to either inclued or exclude internal garages / conservatories and the like in the envelope.
Question: Can you exclude glazed hallways which arent conditioned, but are insulated (eg floor / roof)
Clause 2.3.1 talks about insulating only “Conditioned spaces”, which we take as being heated / cooled.
My home (built 2008) has its living areas separated from the bedrooms and all other rooms in the house by a glazed hallway and enrance with a polycarbonate roof. Consent was given, although it purhaps shouldnt have been at the time H1 was still required to be complied with.
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Bhavna Prentice:
June 9th, 2010 at 9:16 am
Hi Jeff,
That is tricky, I imagine it would fall under an Alternative solution, and you could show by insulating the entire thermal envelope of the two separate areas you meet compliance. But as with any Alternative solution you need to be able to prove this to your local council. Another option would be using the Modeling Method particularly if the total glazing is greater than 40%.
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Jeff Lummis:
June 9th, 2010 at 10:47 am
Thank you for your response. Do you know what it would cost to have a consultant complete calcs using the modelling method? A broad range would suffice (for a residential home).
Another case,
I have a client who has a two storey small semi-detached home. The lounge is extended across the entire northern side with bathroom / kitchen / bathroom and entrance on the south. Upstairs there are two bedrooms.
My client wants to install a conservatory across the entire width of the north side. The conservatory will need to be separated from the house with an intermediate wall & with openings. An opening width (with a sliding doors) of around 63% of the wall length (approx 8.3m) is wanted. The modelling method once again would be needed (probably at a cost of more than Building consent itself) Comments welcome here…….
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June 8, 2010 at 2:02 pm
Hi Bhavna
When looking to increase the insulation in a house ceiling that already has insulation fitted between the ceiling joists, it is possible to lay more insulation over the top.
Saying that the original insulation value is R2.2 (glass wool), what would adding another layer of the same do to the construction insulation value – i.e would it effectively double it?
(I am looking for a value to input in the calculation method)
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Bhavna Prentice:
June 8th, 2010 at 2:44 pm
Hi Jared,
It sure would, basically its all linear and you can effectively add the R-values together. In reality there maybe a small amount of compression of the product on the bottom, reducing its R-value slightly. From NZS4859:2002 this would be a 0.5% reduction in R-value for every 1% reduction in thickness.
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June 8, 2010 at 3:28 pm
HI
Thanks for your answers, Is foil an accceptable solution for underfloor insulation for a timber floor?
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Bhavna Prentice:
June 9th, 2010 at 9:15 am
Hi,
As foil itself does not have an R-value and the R-value is achieved by the airgap, the Construction R-value this produces varies for different constructions, according to the BRANZ House Insulation Guide this is R1.1 for a foil with a 100mm drape. This does not meet the R1.3 required, however some homes with an enclosed subfloor and a certain area to perimeter ratio can come up to a total construction R-value of R1.3. So while it can meet the requirement of the Schedule method, it does not for all timber homes.
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June 8, 2010 at 5:28 pm
Hi,
I am currently designing some townhouses with a basement garage.
Firstly should i be including the basement in the H1 calculations.
Secondly i have gone through the calculation method excluding the basement and my building complies by quite a bit however i cant get the concrete floor to comply with the 50% minimum R value for a floor. Do you know any way around this without using the modeling method (as i have got a similar buiding to comply in this situation by having a consultant to model it)?
Cheers
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Bhavna Prentice:
June 9th, 2010 at 9:24 am
Hi Craig,
In this case, insulating the concrete slab with a product such as our Pink® Batts® Commercial CosyFloor® would allow you to meet the required R-value. The Pink® Batts® Commercial CosyFloor® 50mm product provides an R-value of 1.5 and is simply fixed to the underside of the concrete slab using Insul anchors.
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David Curl:
June 11th, 2010 at 11:28 am
Hey Craig
Branz have a program called ALF which will do what you require, without the consulants charge. It will take time to input correctly all the required data so strapping and lining the lowers slab would be less problematic.
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June 9, 2010 at 8:43 am
Hi Bhavna
We are working on a commercial project at the moment that requires an R value of R1.9 in the roof. We are planning to use Sisalation medium duty 430F on sfety mesh fixed to the underside of the purlins and placing Bradford Gold insulation between the purlins.
Bradford Gold Ceiling is available in R1.8, R2.2 and R2.7. My question is which insulation will meet the R1.9 requirement considering the insulation is broken at each DHS purlin.
regards
Neal
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Bhavna Prentice:
June 9th, 2010 at 10:12 am
Hi Neal,
Firstly why would you want to use Bradford Gold, when you have a nice New Zealand made product called Pink® Batts® insulation available?
The Construction R-value achieve will depend on your purlin spacings and size. A simple way to think about this is based on the percentage area the purlins take up eg: 15% of the Roof area. I’ve put together a quick example to illustrate this below.
• The R-value of a 250mm DHS Purlin is 0.005 (based on a k-value of 50 W/mK)
• If you installed R2.2 (85% of the Roof area) its contributing R-value would be R1.87 (2.2 x 0.85)
• The Purlin would offer R 0.00075 (0.005 x .15)
• Total construction R-value would be 1.87075 m2K/W, including the lower R-value of the Purlins.
I hope that helps, and if you need any more information on the Pink® Batts® range of products available please download our current product guide. http://www.pinkbatts.co.nz/assets/Uploads/PDFS/Pink-Batts-Thermal-and-Acoustic-Insulation-Product-Guide2.pdf
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June 9, 2010 at 8:40 pm
Hey all. Section 112 of the Building Act 2004 requires building undergoing alterations to continue to comply after the work is done to the same degree as before the work to the vast majority of Code Clauses. If you have an uninsulated house at present, you do not have to insulate the building to meet current H1 code standards. Throwing R1.8 in the wall and ceiling will improve the situation, which is more than what the Act calls for. Jeff Lumis…. Class your conservatory as unconditioned space and show the intermediate wall achieves the same level of insulation as the current building has and no BCA can deny your consent. Mr Ackerman, you need to add the R Value of the soil to the R1.1 value given in Bhavna’s response. Normally draped foil 100mm + the soil R Value achieves R1.3.(Comment 4 Table 2a H1/AS1) The minimum R Value usable in the Calculation method is 60% of the figure given in H1/AS1. Therefore standard single glazed windows cannot be approved under the Calculation Method, Only Building Performance Index assessment. Craig See table 2a Comment 4 H1/AS1. Concrete slabs comply.
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Craig:
June 10th, 2010 at 5:19 pm
Hi David,
table 2a comment 4 H1/AS1 refers to slab on ground complying. In my case i have a 150mm thick suspended concrete floor which i believe gives me an R value of slightly less than the R0.65 minimum for a floor using the calculation method.
Do you read comment 4 to included this as complying as well?
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David Curl:
June 11th, 2010 at 7:26 am
You are correct Craig, the Table 2A comment is for slab on ground. What I see for suspended concrete flooring systems is Pink Batt Snug Floor or other bulk insulant as a layer beneath the slab. Think of it like heated air is a teenage boy and cold air is an extremely sexy siren What you are trying to do is slow down the passage of heated air to cold air. The problems with slabs is the unprotected edges which leak heated air like a sieve.
Personally, I would never consider a suspended concrete slab. There is nothing sustainable able concrete and where there are alternatives they should be used. Concrete floors are colder than timber floors and the fallacy of heat sinks have been proven to be false. But by lining the underside with bulk insulants, you will achieve a very good result which complies.
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June 9, 2010 at 9:00 pm
Standard single glazed windows have a R Value of R.13 according to the superseded H1/AS1. The R0.16 assigned by Brahvna is not justifiable. And as 60% minimum is permitted for the Calculation Method, I doubt it would pass Consent checking. That is if the BCA if checking H1 or just giving it lip service.
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June 11, 2010 at 12:12 pm
David I agree with what you are saying, but does it really matter. With the skill level of most tradespeople on site and due to the fact that 99% of clients want the cheapest job, the result is short cuts and substitution. Plans can specify R3.6 ceiling batts contractors can use R3.2 how can you verify on site. result cheaper building, client gets a bargin. The big question is you reap what you sow, hence I do not care if New Zealanders want to live in cold damp houses, pay monkeys get peanuts.
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June 15, 2010 at 9:33 am
I am enjoying reading this blog. My concern is where specifiers are trying to achieve the “minimum” R values required. Where can we find information on return of investment when buildings achieve much greater results than the minimum our building code requires.
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June 16, 2010 at 3:40 pm
Hey Bhavna,
2 Questions for you. The first is an easy one.
1. If ceiling insulation needs a minimum of 25mm cavity to allow for condensate to vaporize and flow away, does wall insulation need the same? It seems problematic to me that wall insulation is pressed up against building paper in non-cavity systems.
2. We are building a studio with a skillion roof with exposed wishbone trusses with T&G sarking. The current design involves 90 x 45 dummy rafters installed over the sarking with 70 x 50 purlins to act as both fixing for the CGI and as a cavity to remove condensate. Does pinkbatts ceiling insulation need nogging between the rafters to support the insulation and stop it from slipping as the roof pitch is 35°.
Thanks for you time.
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June 16, 2010 at 7:06 pm
Tim West it would be good to know what insulation you propose to use in the ceiling space where you have approx 110 mm in height to play with.
Regarding cavity in the wall it will be interesting to see the reply you ask for.
Neil your comment is well put together regarding designers builders etc only wanting the min. From experiance I have found that good quality insulation that is installed correctly has an excellent pay back period, but you need to be well above the min required. For example two laters of R5 ceiling batts, one layer between the trusses the other laid at right angles to the first layer and cover the bottom chord of the trusses etc.
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Dean Buckeridge:
July 1st, 2010 at 11:03 am
John,
I agree that we should be thinking well above minimum insulation levels but my experience tells me that most designers do not understand sufficiently how insulation works in terms of a whole of building solution and how to get the most effective insulation envelope for your clients money.
I have done a lot of reading and observed the outcomes of an experiment using the ArchiCad program on a model which demonstrated clearly that the most effective way of increasing the thermal performance of a building was to address the weakest areas of the envelope first.
These are firstly holes in the envelope such as down light penetrations and uninsulated slab perimeters, and then once those are addressed the worst performing part of the envelope is always going to be the windows. You will achieve much higher performance with standard insulation levels to walls and ceilings and bringing the windows up, and the lowest performing part of the windows is the aluminium frame, so thermally broken joinery (or PVC or composite frames) should be the first upgrade and once these are addressed then look at upgrading elsewhere.
The analogy I make is to compare the insulation envelope of a house with a sleeping bag. Would you buy a top grade down sleeping bag and cut a series of holes in it (representing downlights etc) and expect it to keep you warm in sub zero conditions? No, of course not, it would leak heat so fast it would be unbearable, but by comparison a moderate standard sleeping bag fully intact would be much warmer.
The other aspect that we generally don’t consider is that as we improve the insulation envelope and lose less heat through conductivity the heat losses through uncontrolled air movement through the building become proportionally greater and therefore more critical. It is worth googling Lothar Moll for this, he is a German building physicist who was out here recently talking about this. For well insulated buildings I believe we need to be looking at rigid air barriers to help control this, Lothar also advocates using a wrap system on the inside of timber framing to prevent moisture from inside the house entering into the framing.
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July 26, 2010 at 7:51 pm
Hi Bhavna,
Could you advise me which method would best suit a Hotbloc house with 33% double glazing please?
Thankyou!
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July 27, 2010 at 10:02 am
Hi Hans,
The Calcualtion method will be the the most appropriate, using the Construction R-values Firth provide with their Hotblocs.
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August 2, 2010 at 1:05 pm
Hi I have been asked to do some H1 calculations for a house that is about to double in size, and not to sure how to go about it?. I sthere a certain spread sheet that you have to use to the calculation on?. How do I go about finding out where to get information on this?
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bhavna prentice:
August 2nd, 2010 at 2:03 pm
Hi,
Have a quick look through this it should point you to the right resources
http://www.pinkbatts.co.nz/assets/Uploads/PDFS/Pink-Batts-NZBC-H1-Energy-Efficiency-Guide.pdf
The link to the spreadsheet is also in the main post.
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September 28, 2010 at 12:42 pm
Hi
Could you please tell me which insulation we should specify for hot water pipes?
foam polyethylene, high density fibreglass with plain/calico or aluminium covering, foam rubber or hair felt?
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September 29, 2010 at 6:02 pm
Hi Bhavna
Can you clarify for me what I would need to do in the instance where an existing house that does not meet H1, is in the process of being altered, and the alteration works figures are better but do not meet H1 also? Or is this seen as sufficient enough?
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jeannette ellis:
October 4th, 2010 at 4:26 pm
tony i have done quite a few alterations now with H1 complance. The trick is to know what you are altering. If it it a pure addition. H1 complance needs to be only for the new external envelope. (ie wall that is joined to the existing complies as is, as existing building complies, no matter how bad the insulation is.) if you are putting new windows into existing exterior walls it will often fail,as even an existing uninsulated wall has a better R rating than a new double glazed wndow. In this case you will have to trade off with some insulatin to the existing stucture. I use design navigator for all my calculations (appologys to Batts) none of my efforts at calculations in alterations have been rejected, yet.
If you are doing improvements to an existing structure, any improvement in thermal resistance would be welcome, even if you can’t prove compliance.
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David Curl:
November 21st, 2010 at 1:59 pm
The DBH, the people in charge of writing and administrating the code and The Act, are pushing a risk based assessment by the BCAs. This means if your building is a single story simple shape residential house, the risk of failing is low and the BCA should only need to do a cursery glance check of it. Why I am bringing this up is if building being renovated is just such a simple building, more than likely the BCA will not care if the insulation does not comply. They will allow it to go through.
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October 1, 2010 at 9:38 am
Hi Bhavna
I have completed several H1 compliance submissions using the BRANZ Calculation spreedsheet available from the BRANZ Toolbox. http://www.branz.co.nz/H1-support
Also wish to point out an error in your worked example.
You have used the floor R value from the 140mm stud frame line (1.8) rather than the 90mm stud framing line (1.6)
Using the correct floor value means the ammended insulation version still fails.
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bhavna prentice:
April 18th, 2011 at 8:53 am
Thanks Clive – I will look into that
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April 15, 2011 at 5:29 pm
Hi Bhavna
I recently lodged a building consent application for a project which consists of 4 retail buildings all under 300sqm GFA and heavily glazed.
Since the buildings are under 300sqm, NZBC H1/AS1 refers to NZS4218:2009 which requires insulation values equivalent to that required for housing. The flow chart at the front of NZS4243:Part1:2007 also refers buildings under 300sqm to NZS4218.
When I sat down with the building officer to lodge the consent I had a discussion with him about this as and he told me that If I read NZBC H1.3.1 there is a distinction between commercial and housing. He pointed out the notes beside H1.3.2E stating that these clauses ‘only apply to housing’ and therefore performance index requirement of 1.55 that NZS4218:2009 is designed to achieve is not relevant for Commercial buildings and clause H1.3.1 which does not have any specific performance index values is relevant to commercial buildings.
Performance
H1.3.1 The building envelope
enclosing spaces where the temperature
or humidity (or both) are
modified must be constructed to—
(a) provide adequate thermal
resistance; and
(b) limit uncontrollable airflow.
If this is the performance requirement for buildings other than housing, would it not sound feasible to propose compliance with this performance requirement as an alternative solution. The argument/evidence to back up the alternative solution would be the old building code performance requirements before the additional clauses were added for housing and based on clause H1.3.1
Interested to hear your comments.
Thanks.
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David Curl:
April 17th, 2011 at 1:59 pm
Insulation is all about minimising the amount of non renewable or depletable energy by stoppin heat from escaping. It recognises that residential houses are the number one source because people occupy them during evenings and night time, when it is usually colder. That is why residential houses must meet stated performance.
Commercial need to satisfy Clause H1.2, H1.3.1, H1.3.3, H1.3.4 and H1.3.5. Although no figures are given, if the commercial buildings you design are cheaper for your tennants to occupy, due to lower energy use, then the amount the owner can charge for them is greater. (Instead of the power companies getting the money, the owner is.)
But I dare say, very few buildings will have there lighting properly designed and insulation provided to fully gain efficiencies.
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Glen:
April 18th, 2011 at 9:33 am
I agree with what you are saying David, and I always insist on maximising insulation particularly in residential. However, retal buildings require large areas of glazing and it becomes problematic when this building type is required to meet the same insulation standards as housing. We ended up getting a thermal model of the buildings done and to comply we have had to add 90mm strapping with R2.4 insulation to inside face of all precast walls, R3.6 roof insulation, and dark tinted argon filled double glazing. To me, this seems a bit excessive for retail – how many shops do you know of that have dark tinted argon filled double glazing. This has major implications on the cost and overall feasibility of the project.
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David Curl:
April 18th, 2011 at 4:29 pm
The cost up front will always be less than the ongoing cost of energy use to heat the building. And in some cases I acknowledge the trade off will not be economic. But suggest to thr owners that money given to the elctricity companies could be channelled into their pockets, and see if they are keen to learn more.
An example of eco commercial buildings I am aware of was designed by Alisdaire Daines of Nelson. His figures are very compelling for any property owner.
April 17, 2011 at 2:34 pm
Well written your comment above regarding insulation. I have been saying for some years people only understand the items they can see and why waste money on the items they can not see like wall insulation. It is only when you live in a well insulated house with very little energy being used for water and room heating most get the full picture. The same applies to commercial and industral buildings. People need to remember good insulation and lighting works well for both the summer anmd winter months.
Keep up the good work Mr Curl.
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April 18, 2011 at 10:20 am
There are some very valid comments here, and I agree with David and John about the whole approach to H1 compliance.
Perhaps while H 1.3.1 can be interpreted as having no set performance requirments, the methods of verifying you have met H1 are fairly well laid out in the H1/VM1.
Excert from H1/VM1
1.0.1 For determining the insulation
requirements of the building envelope,
buildings other than HOUSING are classified as
being either small or large. A small building is
any building with a net lettable area no greater
than 300 m2. A large building is any building
with a net lettable area greater than 300 m2.
Note that NZBC H1.3.1(a) (temperature and
humidity control) does not apply to assembly
service buildings, INDUSTRIAL buildings,
OUTBUILDINGS, or ANCILLARYBUILDINGS.
But as Glen proposes there may be Alternative solutions available, but proving these meet current H1 requirments could be difficult.
Not sure if that is useful Glen, but thought I should add my 2 cents worth (perhaps given the current econmic climate, I should say 10 cents)
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