Heating Assessment Tool

[Adam Reid]

Hi Everyone,
Hope you are all keeping sane during the lockdown.
I was just wondering how many people have tried out the Heating Assessment Tool on the tenancy services website https://www.tenancy.govt.nz/heating-tool/ and how people are finding the sizing recommendations for different parts of the country?
My initial experience from calculations on my own home and feedback from colleagues is that the recommendations seem a bit higher than necessary. Heat pumps and log fires which have proved perfectly adequate in the past are less than 90% of the recommendation- meaning that top up heating would need to be installed in a rental situation to meet the Healthy Homes Standard.
Here in Christchurch the calculation is based on the heating requirement at -4 degrees C which may be part of the issue. It also raises another question when assessing the existing heat pumps. How does one find out what the heating capacity of a heat pump is at -4 degrees C (or -10 C if you live in the McKenzie District)? The rated output of the heatpump stated on the unit is based on 7 degrees C so is irrelevant.
I also noticed on the schedule there seem to some anomalies in the temperatures used in different districts. Wellington (2 degrees) is warmer than Auckland (1 degree), Kapiti (-3 degrees) and Porirua (0 degrees). I am sure Kapiti residents would be surprised they are 4 degrees cooler than those living under the snowcapped peaks of Kaikoura (1 degree).
Anyway keen to get some feedback from others around the country who have tried out the tool.
Regards
Adam

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[Vicki Cowan]

I’ve prodded a couple of people on this one too, Vicki

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[Vicki Cowan]

Hi Adam,
Richard Popenhagen, Nelson City councils EDA has kindly had a little look through.
Here’s his email to me (happy for me to re-post here!).
Vicki

Hi Vicki

I haven’t had cause to use the tool to date, so I took a look today to familiarise myself with it, in an attempt to understand the questions raised.

Regarding the temperatures to be used for different districts, these are set in Schedule 2, Clause 5: Assumed external temperature, in the Residential Tenancies (Healthy Homes Standards) Regulations 2019: http://www.legislation.govt.nz/regulation/public/2019/0088/latest/LMS160629.html#LMS160629

As to how these figures are derived, this question should be addressed to the Ministry of Housing and Urban Development: healthyhomes@hud.govt.nz. I am sure there will be a metrological basis these are derived from, maybe the coldest temperature that district is likely to experience in winter? Bear in mind that in every district there can be quite varying micro-climates and temperatures across relatively short distances (north side of a hill verses shaded southern valley), so the temps in schedule 2 are a fairly blunt instrument. As a precaution, maybe anyone doing the calculation should err on the side of caution and use the worst case scenario? (refer to comments below about what temp to heat too).

Whether the required heating calculation output is higher than people believe it should be is subjective (and somewhat irrelevant). It is what legislation states you must achieve, and unless/until someone is going to effect a change to the regulations, that is what the law sets as the minimum level of heating that must be provided.

The other point I would make is that the calculation is to only take that living area to 18oC. Try living in your home at only 18oC all winter, most people would find this still too cold. WHO recommends a minimum living room temperature of 20oC for homes with young children, elderly or unwell people. 20oC to 24oC is the temperature most people find comfortable for their living room in winter. Having a little bit of extra capacity to give people a choice of what temperature they want to heat their house to in winter is not a bad thing. Indeed, as I search further into this I found this statement: It is important to note that devices capable of heating a living room to 18˚C on the coldest days, which is the requirement under the heating standard, will be able to heat a living room to higher temperatures most days in the year. https://www.hud.govt.nz/assets/Healthy-Homes/765404e8a3/Healthy-Homes-Standards-Common-Questions-and-Answers-13052019.pdf

In regard to heat pump capacity:
To reflect a variation in capacity depending on outside temperatures, heat pumps can have three heat capacity ratings. These are based on standardised testing under laboratory conditions.
• H1 rates the unit’s heating output when the outside temperature is 7°C.
• H2 rates the heating output at 2°C ambient temperature.
• H3 rates the heating output at -7°C ambient temperature.
These ratings allow you to select the appropriate heat pump for the climate and household requirements (i.e. the design temperature and heating load) of individual situations. (From: http://www.level.org.nz/energy/space-heating/heat-pumps/)
So, although most heat pump capacities (and COP) are published using the H1 figure, in colder districts you need to ask the manufacturer what are the H2 or H3 figures that match the climate you are installing into.

A quick review, come back to me if you want any further comment

Cheers
Richard

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[Ian McChesney]

Hi Adam
You raise an interesting point re the heating tool, and I have heard similar sentiments from elsewhere.

Last year, while the Healthy Homes Standards were still in draft stage I went through an exercise comparing the heating requirement of a hypothetical room using the draft methodology outlined in the HHS discussion document with a number of ‘methodologies’ that were used to size heaters by heat pump installers, some energy advisers (including CEA) and Consumer NZ. I used the same criteria for all e.g. the internal room temperature was 21C for all. At that stage the draft HHS heating calculator was resulting in a heater size typically 10-20% larger than the other methodologies. However, I haven’t gone through the final HHS methodology to see whether there have been changes, but neither have I verified the various ‘rule of thumb’ methodologies that have commonly been used by heat pump suppliers/advisers.

By and large I agree with Richard’s points but would comment on a few things:

1. I think extra capacity in heat pumps is generally a good thing, for the reasons Richard outlines, but I can see the issues caused when existing heat pump installations that up until now have heated the room satisfactorily are deemed too small under the HHS heating tool. It seems to me that the solution offered under the regulations – installing supplementary resistance heating up to 1.5kW – may not much of a solution at all and in some situations could be quite retrograde.

2. Regarding the information requirement to check heat pump outputs at the various external design points i.e. -4C for Christchurch, and variable throughout the country. This is not necessarily readily available information especially for existing heat pumps, and it boggles the mind that this information will need to be accessed in order to sign off compliance for each individual installation. I think there is a strong case to request Government post this information online for the main heat pumps sold in the last 10-15 years. I’m sure this would save a lot of time/duplication of effort from those checking compliance. Previously the EnergyWise site used to have a database of heatpump performance – can this not be re-purposed and expanded to meet the need here?

3. Indeed, as Richard says, the healthy homes regulations sets the legal requirement, so right now that’s it. I would note however that this particular regulation – the heating standard – is potentially at threat. The National Party last month promised, should they be the government at the next election, to repeal the heating standard of the Healthy Homes Regulations, including the requirement for a heater to be installed in living areas, and the requirement for a specified heating output. No doubt they have support for this view from some landlords. Personally I think this would be a hugely retrograde step, having advocated for years to get heating standards in place. Nevertheless, if there are genuine concerns about what the current standard specifies, it might be useful to air these (internally). Amendment of a regulation, sooner rather than later, is infinitely preferable to repeal.

regards
Ian

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[Adam Reid]

Thanks Richard and Ian for your feedback,
Some interesting points there.

I totally agree with Richard’s point that 18 ℃ is not a comfortable living room temp by any stretch of the imagination. But I would like to share a couple of personal examples of why I feel the calculations don’t necessarily fit with my practical experience. Bear in mind when reading that I am the sort of nerd who is constantly checking my indoor /outdoor temperature to see how things are tracking so I have a pretty good handle on how my heating is performing.

1) In my own home my 7.5kW log burner can heat the living area to 25 C plus even in the coldest weather and I have to let it burn down after 3-4 hours use as it becomes uncomfortably warm. I consider the burner to be excessive. Yet if I wanted to rent my house out, I would have to install additional heating to meet the 8.6kW required by the tool.

2) At my rental property (where we lived until 18 months ago) we have a 6kW heat pump which we are happy with. It is a small 2-bedroom house with both bedrooms opening off the living room. We always left the bedroom doors open (more than doubling the area) and were able to heat the whole area to 21 ℃ quite comfortably in most conditions. On frosty mornings the heat pump did struggle, and the indoor temp might drop as low as 16-17℃. As these conditions only ever lasted for a couple of hours it was more of an inconvenience than a hardship. According to the tool we require 4.9kW of heating for the living room alone, discounting the bedrooms. I know the H2 output of the existing heat pump is 3.95kW so only around 80% of the requirement. I don’t know what the output at -4℃ is but I think it is safe to assume that it will be less than 3.4kW so will require replacement of the heat pump as it would need more than the maximum 1.5kW of top up heating.

I know the heating standard is something people in our group have advocated for over many years and it is fantastic to see this being implemented. It would be a great shame if an aspect such as incorrect sizing was to provide ready ammunition for those who oppose the legislation. I think if the tool is not right, we risk alienating the good landlords who already have good quality heating installed by forcing them to replace existing heating or install inefficient and unnecessary top up heating

I think Ian’s suggestion that the government publishes a list of the outputs at various temperatures is an excellent idea. I know from experience that heat pump manufacturers are not always eager to share this data. Having a published list would make this much easier for assessors trying to determine if an existing appliance meets the criteria.

One point I think it is important to make is that oversizing of heat pumps is not always a good thing. Oversized heat pumps tend to switch off and on more frequently, run less efficiently and consequently use more electricity than a unit which has been sized correctly. They can behave more like an old fixed speed unit rather than an inverter and the frequent on off cycling tends to wear the units out more quickly My main concerns about this are…

a) Some grossly oversized heat pumps were installed in Christchurch as part of the heating replacement scheme following the earthquakes. I have seen more than one instance where people have found their oversized heat pumps performing poorly, too expensive to run and simply don’t use them. This would be the worst possible outcome for vulnerable tenants.

b) Each heat pump manufacturer has specific guidelines for sizing their heat pumps which they train their installers to use. Will heat pump manufacturers honour the warranty on a worn-out compressor if they deem the unit was not correctly sized in accordance with their specifications?

Regards

Adam

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[Felix Gonzales]

Hi everyone, I just want to check with rest something related to this.

For Auckland, relevant outside temperature is 1C to determine the heating requirement. Is it also everyone’s understanding that it also is part of the requirement when determining the right heating device? I guess this is more a question for heatpumps, as it’s the only heating source whose heating output is affected by the outside temperature.

Another way to ask this if in Auckland, if I determined through the calculator, that I need 4kw of heating, using a heatpump with a 4KW published heating output (which is an H1 – 7C) is definitely not going to be compliant? Using H2 (2degreeC conditions) is very much closer but really still do not meet Auckland requirements?

Thanks.

Felix

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