We’ve been asked by multiple folks how to use the Passive House Planning Package (ie PHPP v9.6a) to show building code compliance in accordance with the new H1/VM1 5th edition. You can do this as MBIE made two key changes to enable use of PHPP
- remove requirement for multi-zone models D.1.6.2 – note this has limitations
- internal loads comment under D.4.3.2
There is still one ‘large’ block and that is NZS4214. Luckily we can use ‘smooshed constructions’ which give you the same results for NZS4214 and ISO6946. [Geek note – NZS4214 calculates the R-values of a non-homogenous construction in a way to obtain the lowest R-value; ISO6946 calculates the R-value two ways and averages them; Luckily both methods yield the same result if the material is a homogeneous layer.] Instead of entering timber fractions etc for your reference building just enter a ‘smooshed’ material which is all the same stuff. Then if you want a R2.0 reference wall you take away the surface films R2.0-R0.12=R1.88 you can simply enter into the PHPP U-values calculator a 100mm thick layer of material with a thermal conductivity of 0.0532 W/(mK) which is 0.1m/R1.88. This can be done similarly for roofs and suspended floors as needed.
You still need to match the other stuff like glazing ratio, take out the skylights, etc but an actionable checklist below and you’re done. I’d like to thank PHINZ for involving me in their discussions with MBIE on this as we’ve been working with MBIE and the building industry on the slab-on-ground calculations for a while now. I’d especially like to thank Christian Horning of MBIE, Dr. Kara Rosemeier, Elrond Burrell and Guy Shaw from PHINZ for their discussion – this document has resulted in part from discussion with them.
Below is our internal checklist we used to develop our process for building the models. Please let us know if you see any place where it is incorrect and we’ll fix it (and we’ll thank and credit you).
Both models: [We’d suggest using two variants in a PHPP file but you could use two copies of the PHPP.]
You are comparing the sum of the heating and cooling energy consumption (kWh/sqm/year); You need to turn on mechanical cooling for both models.
External reference areas are acceptable as NZS4218 is no longer referenced; Use external reference areas like you do for Passive House already. The slab-on-ground A/P ratio to use the tables from H1/AS1 needs an internally measured A/P ratio but there is an easy conversion shown below.
Any summer night/day ventilation etc should be the same in both models.
Set ventilation for MVHR to 0.5ACH – you use the same MVHR in both models (or no MVHR in both).
Infiltration same as proposed (same airtightness)
Glass SHGC or g-value the same as proposed.
Heating and cooling equipment must be the same (same COP) in both models.
Proposed building:
Model per the design documents with notes above; we use our standard designPH process like any high-performance project.
Check the proposed building has the correct PSI value for the proposed slab edge.
Window installation PSI set to zero; Any other thermal bridges should be included if they are higher than the reference building. An example of this is if you had an attached garage. You would need to have the PSI value to the garage in the proposed building.
For slab-on-ground model it the Passive House way – you MUST use a specific PSI value for the slab edge in the proposed and account for any attached garage, porch or unconditioned space via a PSI value unless it has the same slab edge insulation under the connecting wall.
For slab-on-ground with raft style slabs please follow the process for floors described here: <link https://sustainableengineering.co.nz/entering-waffle-pod-slabs-into-phpp/> Note you CANNOT use the R-values for the floor slab-on-ground elements in PHPP from the HPCD or the H1/AS1 tables directly. PHPP deals with slab-on-ground floors in a very flexible manner but this means you need to enter only the layers of materials making up the slab-on-ground such as the concrete slab and any underslab insulation. Then PHPP calculates the additional benefit of the ground in reducing heat losses through the floor based on the slab-on-ground dimensions and the climate (plus heating season and other factors which is why it’s hard to tabulate).
Reference building:
Skylights set to zero
Glazing area to 30% of external wall area (yes this means the PHPP external wall area + all the Glazing area); Must be no more than 30% – can increase it to 30% in the reference building if you want provided the reference building is less than 30%. This is most easily done by changing the window quantity down or up. Yes PHPP can handle 1.1 windows as it’s just multiplied internally. [cool tricks like this are our specialty]
Note that glazing area is the full window area (glass+frame) and includes glazed door area (glass+frame) but excludes skylights and opaque doors and panels.
Opaque door/panel area that is no more than either 6 m2 or 6% of the total wall area set to R-value for reference windows and doors (or left higher) over that, reduce the opaque door/panel area in the reference building to 6m2 or 6% of the total wall area.
Window R-values set to climate zone value by adjusting frame and glass U-values. [Suggest not changing the frame heights or the Uf as this can move the building in lots of directions; Change the glass Ug to make the average windows U-value=1/R-value required; Leave the SHGC or g-value the same as proposed.]
Window installation PSI set to zero; Any other thermal bridges PSI set to zero (excluded slab-on-ground perimeter PSI which MUST be included see below);
External shading devices such as fins and overhangs may be removed
Walls to smooshed R2.0; Roofs to smooshed R6.6; Suspended floors to R-climate zone; Slab-on-round to compliant slab construction for the A/P ratio and PSI of this slab edge;
For slab-on-ground you need to enter a slab that meets H1/AS1 required R-values for either ‘do not’ or ‘do’ contain embedded heating systems (ie if you have in-slab heating). Again note you CANNOT use the R-values for the floor slab-on-ground elements in PHPP from the HPCD or the H1/AS1 tables directly. PHPP deals with slab-on-ground floors in a very flexible manner but this means you need to enter only the layers of materials making up the slab-on-ground such as the concrete slab and any underslab insulation. Then PHPP calculates the additional benefit of the ground in reducing heat losses through the floor based on the slab-on-ground dimensions and the climate (plus heating season and other factors which is why it’s hard to tabulate). To do this you:
- You need to measure the A/P ratio from the inside of the exterior walls. Either measure directly or convert from Passive House external measurements to internal A/P ratio by use of the equation from H1/AS1 (5th edition, Nov2021) equation F1 and F2.
- Use this A/P_internal to find a compliant slab using either the tables in H1/AS1 (5th edition, Nov2021) or tables to the H1/VM1 (5th edition) from a proprietary system.
- Put this slab edge PSI value (calculate it in Flixo or THERM or look it up from the supplier or in the HPCD) and layers of materials that make up the slab-on-ground floor into a U-value calculation and model this using the ground sheet like normal.
- Remember for the reference building you run the same slab edge insulation (and PSI value) all the way around the slab neglecting any attached garage, porch or unconditioned space.
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Notes:
It is possible that per D.1.4.1 means we can simply go with two variants in PHPP without making any changes to the way PHPP normally operates. This then would not require smooshing and surface resistance corrections. It would be in the spirit of VM1 in that it requires a like-for-like comparison. This would require a determination or some risk (likely low) during consent.
It is possible that per 5.1.1 (b)(v) of 4214:2006 which allows for the use of “computational methods”, specifically mentioning ISO standards allows the use of ISO6946 and we don’t have to smoosh the R-values anyway. This is how it was interpreted for the HPCD Handbook work.
