ALF 3.2

By - , Build 115

The last Build (October/November 2009, page 34) introduced ALF 3.2, a free BRANZ online aid for the thermal design of houses. Questions from ALF 3.2 users continue to flow into the BRANZ helpline, and some common questions are answered below.

Q How do I log in? .

A Go to alf.branz.co.nz and sign up in ‘Create an ALF My BRANZ Account’ (even if you’re a My BRANZ member). After you receive the confirmation email, click log-in at the top right of the screen and enter your email address and password (this is case sensitive). Remember to record which email address you signed up with. You can request and change the password if you lose it.

Q I’m already signed up to My BRANZ, can I use that?

A No, currently the two systems are not linked, so you will need to sign up to ALF 3.2 as a user.

Q I keep putting in the password on the website – why won’t it let me in?

A The password on the website is the serial number to access ALF 3.1, not ALF 3.2. You need to sign up as a user with your own password.

Q What if I lose my password?

A Enter the email address you signed up with and click ‘lost password’. The password will be emailed to that address, so keep your email address current. You can change this in your profile when logged in.

Q When should I use the ALF 3.2 modelling method to show compliance with Building Code Clause H1?

A You can use it for housing of any size or small buildings with a net lettable floor area no greater than 300 m² (see Clause H1 for definitions). It is typically used when the design is outside the criteria for the schedule or calculation methods. ALF 3.2 is intended for stand-alone (detached) designs and should not be used for multi-unit dwellings.

Q Can ALF 3.2 be used for houses over 300 m²?

A Yes, but only for individual housing units.

Q I want to see the difference changes make to the thermal efficiency of my design. Can I use ALF 3.2 for this?

A Yes. When you’ve finished your model, you can create up to 30 copies by going into ‘add another design/or delete an existing design’ on the details page under the project name. You can make changes in each, and see the results and modelled energy savings. You can also rotate the entire model. It’s important to name them appropriately so you can remember the changes in each one. You can also put in an explanation for each model under the design detail section in the details page.

Q My project didn’t save. Why?

A You weren’t logged in. Any work you do is automatically saved when you are logged in.

Q What happens if something crashes while I’m using ALF 3.2?

A ALF 3.2 saves the information you put in at every step. Providing you have clicked away from the box you just filled out, the information should have saved to the central server and be there when you reopen the project.

Q Can ALF 3.2 be used offline?

A Not currently. The advantage with online programs such as ALF 3.2 is they can be updated without users having to download update files. Also, the projects can be accessed from anywhere with unrestricted internet access. The web-based program also supports both Windows and Mac users.

Q Why is my project only giving me the option of selecting the Upper South Island climate files?

A You’re not logged in.

Q The closest climate file doesn’t fit the weather at the site. What should I do?

A You may choose another climate file provided you can justify the change, but it must be within the same region and the same Building Code climate zone. The justification of a change needs to be based on the temperature, wind and sunshine hour profiles. For example, a design in Kelson should use the Wellington (Kelburn) climate file. Wallaceville (Upper Hutt) and Wainuiomata Coast Road (Wainuiomata, Lower Hutt) may be closer than Kelburn but they have vastly different temperature profiles and wind directions than Kelson.

In some areas, the closest climate file must be chosen. Whitianga, for example, has warmer weather than Thames, but because there are no other climate files in the Coromandel/Waikato region that replicate the sun, wind directions and speed, and annual temperature profiles, the Thames climate file must be used. Tauranga’s climate may be similar but it is in Zone 2 and outside the region and so cannot be chosen.

Q How do I choose the floor type?

A Fill out the sections that apply under the floor tab – suspended, concrete or both. Remember that this should only be for the floor backing onto the subfloor space or ground.

To select the type of floor construction and insulation, click on the dropdown menu. This will give you a range of construction types and insulation levels. You can also choose a custom R-value, but ensure that you provide documentation and use the construction R-value.

Q What is the wall thickness in the floor section?

A The wall thickness refers to the thickness of the part of the wall in the thermal envelope that meets the floor (that is, not the subfloor wall). Include interior linings and exterior claddings. Use the closest measurement above what it actually is, for example, if it is 110 mm, use 120 mm. This affects the heat flows through the slab at the point where the wall meets the slab.

Q I want to put a high R-value insulation into a skillion roof. Why does it say I’ve exceeded the limit?

A The construction selected has a limited depth. Typical insulation types can’t meet the R-value specified and fit the cavity space.

Q Can I use glazing other than double glazing?

A Yes, but to meet the BPI, the design must meet an overall level of performance. This is easier in warmer climates and harder in cold climates. Where one element’s performance is low, others will need to be improved. So, if one element’s performance is high, it may be possible to pass with reduced performance of other parts of the building, such as glazing.

Q What do I do with proprietary products?

A You can enter them as a custom value but you must include verifying documentation, such as a BRANZ Appraisal, manufacturers’ specifications or a NZS 4214 calculation as evidence for the Building Consent Authority.

Q Why does the report say I have a different heating schedule and number of occupants than I selected?

A Clause H1 of the New Zealand Building Code includes standardised assumptions for calculating the BPI. This is to create a level playing field for all designs and recognise that buildings are used in different ways by different households. These assumptions include:

  • a continuous temperature of 20°C throughout the building
  • an air change rate of one change per hour or the actual air leakage rate, whichever is the greater
  • a heat emission contribution from internal heat sources of 1,000 kW hours for the first 50 m² of floor area and 10 kW hours for every additional square metre of floor area
  • no allowance for carpets or blinds, curtains or drapes on windows
  • a shading coefficient of 0.6 for windows (made up of 0.8 for windows and recesses and 0.75 for site shading)
  • occupant numbers linked to the total floor areas:

<120 m2 – 3 occupants

≥120 m2 but <180 m2 – 4 occupants

≥180 m2 – 5 occupants.

Q Why is TBC showing up as a result?

A An input required for that part of the ALF calculation has not been entered. Check to see if everything’s completed. The top section of the PDF report also has the errors.

Q What do I give the Building Consent Authority?

A A printout of the PDF of the report. To access this, once you have got your model completed and are in the correct design, click on the ‘results’ link below the picture of the house in the top right-hand corner of any of the tabs. To download the PDF report, click on the ‘PDF report’ button at the top of the page and open it. You can then save the report as a normal PDF and print it out – plus any documentation to back consent R-values.

Q Where do I find help?

A The first place to look is in the comprehensive help files. These can be opened in a separate tab on the web browser so they can be read while working on the project. They are full of information and tips on how best to model the design.

For more

If you do not find the answer to your question, industry members can call the BRANZ helpline on 0800 80 80 85 and press 1, or the public can call 0900 5 90 90 (0900 calls cost $1.99 a minute + GST).

Download the PDF

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