Last week we worked through the last PHPP worksheet for a Passive House project. Now we look to see if we made the final requirement for a successful Passive House project – do we meet the Specific Primary Energy Demand requirement of 120 KWh/(m2a) maximum?
Let’s assume that we got close, but we are not yet there, but a few tweaks could make the difference. Perhaps we are off by a lot which might indicate either an unfamiliarity with low energy usage or more likely a really glaring typo. Go back and look over the worksheets that feed into this number. By now you should be familiar with what each one is set up to measure and this can give you ideas for optimizing or finding that typo.
Let’s start with the DHW & Distribution worksheet. Did you accurately measure your hot water pipes? What happens if you change the insulation on the pipes or the location from a cold region to being inside the thermal envelope? Can a design change to re-route the pipes effect the performance?
On the Solar DHW worksheet make sure you accurately modeled your system. What if you increased the amount of solar hot water you can provide? Any water heated this way will be automatically deducted from the PE value demand of water heated with your energy carrier.
The Electricity worksheet is where you listed your appliances and electrical usage. Did you properly declare all the appliances? Are they listed in the right location of either inside or outside the thermal envelope? What happens if you move them or change the way you expect to use them? Would you use the clothes washer with just cold water or will you hook it to the DHW? Can you replace the dryer with a drying closet and re-route an exhaust port of your ventilation system to draw exhaust air through the drying closet? In the upper right hand section of this worksheet did you declare the type of energy carrier you will use for your domestic hot water and space heating? If not, the PHPP will assume you are using electricity.
The Auxilliary Electricity worksheet takes into consideration all the pumps and defrosters that keep the systems working. Even if you are providing your DHW through solar means, the pump needs to be listed here if it is electrically powered. Did you properly list the power needed for each of the different pumps & defrosters? Could you substitute a more efficient one to make a difference in the bottom line?
The IHG worksheet doesn’t have many inputs itself, but it does get information from other worksheets and one of those is the Electricity worksheet. You have the ability to add undeclared electrical usage that might be unique to your project in the “other” section. This gets referred to the IHG for calculating any interior heat gains. If you know you will be using an electrical appliance that needs to be declared, be sure to list it so the heat it generates is also considered in the operation of your project.
The Compact worksheet is affected by the coefficient of performance of the system you are using for your heat pump. What happens if you use a more efficient system? Did you remember to enter the information about a subsoil heat exchanger to pre-warm ambient air to help defrost the SHX if your project is using one? Don’t forget to record any solar DHW used for space heating on this worksheet too.
The District Heat worksheet only has space for solar used in heating (don’t forget to record that if you are using district heat!) as well as the Utilization factor of the heat transfer station.
The Boiler worksheet needs to know what energy carrier you are using for your boiler. This could impact your PE value depending on what type of energy you are using. You can try changing from an oil based boiler to another type and see what it does for your PE value. Be sure to mark the solar hot water value on this worksheet if you are using that in conjunction with a boiler.
That just leaves us the PE Values worksheet. You can see that each of the sections focuses on the efficiency of the mechanical use and the energy carrier. Be aware of the equipment that is available to assist you in efficiency. Also notice that the last section of this worksheet has a place for recording the amount of energy that is generated by Solar Electric panels. If you are generating power this way the Specific Primary Energy amount will be reduced to reflect you not having to bring energy to your meter. Passive House requirements do not give use credit where you can then use more electricity because it is technically “free”, but it does consider you did not haul that power with resulting losses from a distance.
If you have gone through all the worksheets and are still not quite hitting the mark – give it another look. The more you understand the PHPP and what it is designed for the more you will be in tune with where you can make changes or look for errors that you might have made in entering information.
I hope you have found this series on the ABC’s of the PHPP useful. Up next I will be discussing humidity, moisture, and a project that I am designing that will be in a Marine 4 environment that is practically a temperate rain forest.