Can a Single Mini-Split Heat and Cool a 100m2 Passive House
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My presentation at the 22nd Passive House Conference in Munich , 09.03.2018.
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Can a Single Mini-Split Heat and Cool a 100m2 Passive House
- 1. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 Presentation: Can a single 2kW Mini-split heat and cool a 100m2 passive house? Stefan Pallantzas Civil Engineer NTUA, CPHD, Certifier
- 2. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 “During full summer heat, the house will lean heavily on its energy recovery ventilator to reduce humidity and air temperature, but it also is equipped with a 1-ton ductless mini-split air conditioner with a single vent.” Source : http://www.greenbuildingadvisor.com The 204House, in Lafayette, Louisiana
- 3. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 Project location Papagou – Athens GREECE
- 4. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 Project location Papagou – Athens GREECE
- 5. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 TFA: 1ST FLOOR = 85 Τ.Μ. GROUND FLOOR = 30 Τ.Μ. Project description
- 6. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 Specific building characteristics with reference to the treated floor area Treated floor area m² 114,6 Criteria Fullfilled?2 Space heating Heating demand kWh/(m²a) 12 ≤ 15 - Heating load W/m² 11 ≤ - - Space cooling Cooling & dehum. demand kWh/(m²a) 12 ≤ 16 16 Cooling load W/m² 10 ≤ - 11 Frequency of overheating (> 25 °C) % - ≤ - - Frequency excessively high humidity (> 12 g/kg) % 0 ≤ 10 yes Airtightness Pressurization test result n50 1/h 0,6 ≤ 1,0 yes PE demand kWh/(m²a) 85 ≤ - - PER demand kWh/(m²a) 48 ≤ 45 48 kWh/(m²a) 68 ≥ 60 63 2 Empty field: Data missing; '-': No requirement EnerPHit Plus? yes yes yes Alternative criteria I confirm that the values given herein have been determined following the PHPP methodology and based on the characteristic values of the building. The PHPP calculations are attached to this verification. yes Non-renewable Primary Energy (PE) Primary Energy Renewable (PER) Generation of renewable energy
- 7. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 Month TOTAL PHPP MEASURED HEATING PHPP HEATING MEASURED JAN 2016 689,78 619,35 419,00 367,45 FEB 2016 641,25 388,55 398,00 206,57 MAR 2016 397,78 339,80 183,00 141,35 APR2016 218,01 151,35 15,00 5,00 The proposed solutions for heating-cooling The after-heater Total Winter Cost = 366,93 € Per Day = 2,02 € Total Heating Cost = 161,07 € Per Day = 0,89 €
- 8. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 The proposed solutions for heating-cooling The Mini split Month TOTAL PHPP MEASURED HEATING PHPP HEATING MEASURED JAN 2017 413,40 448,24 163,84 217,08 FEB 2017 371,31 336,24 154,35 117,53 MAR 2017 291,18 265,89 88,62 53,69 APR2017 219,41 171,38 23,22 5,09 Total Winter Cost = 307,78 € Per Day = 1,69 € Total Heating Cost = 91,06 € Per Day = 0,50 €
- 9. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 Comparing 2016, 2017, 2018 2018 2017 2016 JAN 2016 JAN 2017 JAN 2018 EXT.TEMP PHPP 8,53 8,53 8,53 EXT. TEMP MEASURED 8,90 6,56 9,37 INT TEMP PHPP 20,00 20,00 20,00 INT TEMP MEASURED 20,00 20,58 20,90
- 10. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 January 2017, Comparing rooms
- 11. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018
- 12. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018
- 13. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018
- 14. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 Mini-split??? Heat pump???
- 15. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018
- 16. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 Heat Pump performance : the mild MED climate is the advantage
- 17. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 Heat Pump performance : the influence ot the thermal mass
- 18. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 Heat Pump performance : the use of eco/silent mode
- 19. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 Heat Pump performance : the passive house concept
- 20. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 Heat Pump performance : the easy distribution
- 21. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 Conclusions • 2KW Minisplits can cover heating/cooling demand in small residences up to 100m2. • Keep always the house between the thermal comfort margins. Use simple automatization. • Try to reach the best performance of the heat pump using the advantages of the passive house concept. • Keep it simple, stupid!
- 22. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 Heat Pump performance : What about bigger houses?
- 23. IPHC22 Munich, Germany Author : Stefan Pallantzas © Passivistas2018 Thank You! Passive House Live in comfort! Save Energy! Save the planet!
Editor's Notes
- When i decided to send this paper for the conference, the idea was to describe and prove that a small mini split unit can heat and cool a residence in warm and mild climates. I was very happy that this was accepted and I’ve started to collect data about the performance of the unit and of the house in general. This was very exited during the last 2 years and I’m sorry to say that you will only see a very small part of the work that I’ve done and still doing in my house, in order to check and improve the performance of the passive house in the local climate. During the preparation of the presentation, and when I was trying to show advantages and disadvantages of the proposal, I’ve realized that nearly everything had to do with Δθ , meaning temperature difference. And that this ΔΘ in our region is our big advantage for PH.
- I’ve also remembered that my first impression about passive house , back in 2009 was an interesting house in Lafayette , Louisiana. A similar climate like ours. And there the cooling period problem was solved by a single minisplit unit.
- For those of you who don’t know the project, The building is located in Athens, which is in the middle of Greece and has a mild climate;
- The building was built back in 1964 the two street façades are looking south-east and north-east. So the orientation was not perfect.
- It consists of two units: on the 1st floor there is a 98.80 m2 typical private residence with 2 bedrooms, a bathroom, a separate kitchen and a living room entrance area. Its layout was not altered much, apart from this wall that separated the kitchen from the living room which was demolished to increase the flow of southern light towards the living room and there is a separate 43.60 m2 storage/boiler room on the ground floor; this one was converted into an office, the HPHI’s headquarters.
- According to (updated) PHPP calculations the energy balance of the building after the Renovation was the following. The heating period was 4 months. After installing the PV , the building is an ENERPHIT PLUS Building, the first certified globally, according to PHI’s data. I have to say here that we constantly update our phpp calculation for the building , according to the measurements that we have. For example we saw from measurements that we need some more heating during winter and some less cooling during summer, because of the lower internal heat gains, as we are a couple which don’t stay to much at home and don’t cook very often.
- So we decided for the winter to do the heating just with a direct heater. We could heat the house only by pre-heating the fresh incoming air via the ventilation system. The heating load was close to 10 W/m2 and a 1 kW heat source could heat the residence. This was done during the first winter with good results. A 1,3 kW after-heater (Figure left ) was installed in the supply air duct. The system heated the residence pretty good and the consumption was as expected in PHPP. The total average load was less than 0,5 kW and never over 0,75 kW. The total consumption for heating was as shown in the table and the total cost for heating was 160 euros.
- During the second winter we decided to also heat the house using only the mini-split in the Livingroom. The thought was simple: if we could cool with one unit, then why can’t we heat with the same unit and reduce the electrical consumption by at least 50? Total heating cost the 2nd winter, 90 euros.
- The calculated average COP was expected to be 3,28, but the real one was a little bit lower. Although this second winter was clearly colder, the average temperature in the living room was over 20,50oC and never under 20oC (Figure 10). So the figures were clearly better using the mini split for heating. The next step was to improve the performance of the unit.
- I remind that we speak of a single minisplit in the living room and as you can see, the internal temperature is the same +/- 0,5 degree in every room of the house.
- The cooling period for the residence started at June 19th and ended at September 9th. The average temperature of the residence (living room) during 1st summer was 25,2°C. The average temperature in the bedroom was 0,5°C higher, but still comfortable. The average temperature in the office was 1,5°C lower. As we have shown in our paper last year , the performance of the unit for cooling was much better. During first summer we mainly used the normal mode of the unit, so the consumption was very low in terms of electricity use. The SEER of the unit was 8,53 ! Total cooling cost 30 euros. Here I have to say that during this first summer we were use to have an internal temperature up to 26 degrees and we were satisfied with that.
- During 2nd summer we’ve mainly used the silent or eco mode of the unit , but with smaller margins of “set temperatures” and the overall performance was better, although the SEER was around 6. Internal temperature was always clearly under 25 degrees celsius. Total cooling cost 45 euros.
- And all this with a single minisplit unit
- So maybe a lot of you don’t know what a minisplit is! I also remember Miwa Mori last year in Vienna saying that Japanese people , who want to have a passive house , don’t want to hear about air conditioning. Well the reality in a passive house in a warm climate is different. Those of you who know how a mini split heat pump works, just forget the way it runs in conventional houses. In the coming slides you will see the difference and of course the importance of Δθ.
- First of all what is a heat pump in a few words? Heatpumps (or air conditioners) don’t generate heat. The heat already exists inside your home or outside. The only different is that in heatpumps we have a Reversing Valve that allows us to chose to move the heat from inside the house to the outdoors (cooling mode) or to reverse the cycle and remove the heat from outside the house to the indoors (heating mode). In a passive house in a warm-temperate climate this need for heat transfer in both ways is lower because of the the lower Δθ.
- Air source heat pumps are relatively easy and inexpensive to install and have therefore historically been the most widely used heat pump type. However, they suffer limitations due to their use of the outside air as a heat source. The higher temperature differential during periods of extreme cold leads to declining efficiency. In mild weather, COP may be around 4.0, while at temperatures below around 0 °C (32 °F) an air-source heat pump may still achieve a COP of 2.5. The average COP over seasonal variation is typically 2.5-2.8, with exceptional models able to exceed this in mild climates.
- The behavior of the thermal mass of the building showed us that we need to keep a constant situation in the building. We have to keep it always between 20 and 25oC and never leave it cool down during winter or heat up during summer. For this reason we have used some simple automatizations. The unit was always on in heating mode, if temperature drops under 20,1oC during winter. It also was always on in cooling mode, when temperature reached 25,1oC during summer. And because of the thermal mass and the operative temperature of the house , the heating/cooling intervals were short and not more than 3-4 during every day.
- Using the eco or silent mode of the unit was often the right way, if the temperature difference inside and outside was small. This was mainly happening during warm summer nights, where night flushing through windows was impossible to cool the house, because of high external temperature and the thermal mass. So it was better to have closed windows and cool actively, with low consumption because of the low temperature difference.
- This very good performance was of course a result of the appropriate shading, the very good airtightness and the expected performance of the ground heat exchanger (ground heat exchanger performance was more than 85% and 12oC during extreme temperature conditions). Of course doors have to be open inside the house in order to easily cool the total space of it. But even with some closed doors the temperature difference was something like 1oC.
- Another solution on the market for better distribution of air is to use the multisplit units.
- Conclusions In a warm and not so humid climate, like the one in Athens, we always will need active cooling in a passive house. This brings us to solutions like heat pumps. For small residences the use of small heat pumps, the so called mini splits (air-to-air) units is the optimum solution. These units have much higher performance than central units. For small residences, up to 120 m2, a single unit can cover the demand If this unit can cover the cooling demand in a warm climate, then it can also cover the heating demand. And this because the building is a passive house, a house that is well insulated, very airtight and with optimum use of solar and internal gains. This brings us to a very important reduction of construction costs (these units are very cheap, easy to install and service) and electrical consumption (because of their good performance and very low losses). The main rule in order to achieve the best performance with mini splits is to keep always the house between the thermal comfort margins (20-25oC) and never leave it cool down or heat up. As this is always the rule in a passive house, it is much easier to reach it with mini splits and some sensors and simple commands via a mobile app. The good results with the use of mini splits for heating and cooling in our climate makes it easier to reach the Passive House Plus and Premium criteria and the NZEB level of the building. The need of energy production from RES is lower and so the cost of installing such a system is reduced. We can easily say that using mini split units in a passive house in warm and warm temperate climates can bring the total construction costs of the building even lower than a Low-energy house.
- For the moment I can assure you that we can even satisfy a Japanese lady! Thank You.