This presentation is Armstrong’s RIBA accredited CPD presentation entitled… ‘Using Phase Change Materials in construction for a more sustainable built environment’ …and is presentation by Add: NameAdd: Title
Phase Change materials are not a new technology, they have been used in various forms since the 1970’s. It is only in recent years that the focus on sustainability and advances in the durability and commercialisation of PCM’s that they have started to be used in construction products.Phase Change materials help to lower energy consumption within a building and maximise the efficiency of a buildings ventilation system.It is important to note that Phase Change materials are not suitable for all project situations, this presentation will outline the limitations and requirements when using PCM in a construction product.
PCM can be used in Active and passive systems when designed in conjunction with the HVAC system to maximize efficiency. From natural ventilated spaces to integrated chilled ceilings most types of HVAC system can be made more efficient. PCM can be used to offset the requirement of air conditioning, therefore saving on cooling energy, and energy costs.PCM optimizes use of regenerativecooling and heating sourcesPCM should not be used as a replacement for insulation, it acts as a thermal storage unit, rather than blocking out or containing thermal energy.NoGoPCM’s should not be used on exterior walls, the solar gain via the walls greatly reduce capacity of the PCM, and thus leave an inefficient system.PCM’s cannot be added to existing “Active” cooling or heating easily. These systems can be adapted when the design of the cooling or heating incorporates PCMPCM cannot replace air conditioning to manage internal humidity, only thermal comfort.
There are different ways of creating the purge strategy to cool the PCM in the evening. The most sustainable is to use the cool night time air from outside the building.
PCM’s provide lightweight thermal massTo create the same thermal capacity as 3cm plasterboard containing 30% PCM you will need 14cm of concrete, or 18cm of bricks.PCM allows high thermal mass properties to be added to lightweight construction, which could not support bricks or concrete.By using light weight construction it is possible to reduce building cost and running cost of the project.
In this graph the red line shows the temperature fluctuation throughout an office space over a week without an installation of PCM material.The Blue line shows the same fluctuations over the week but this time with PCM materials added to the office space.The use of PCM material adjusts the thermal comfort of the room. The very high temperatures of 32°C are not reached with PCM, as the excess heat is stored within the product. This heat is then released at night when the room cools down, so the room does not reach the low temperature of 18°C.This process and ability to store excess heat energy creates an improved temperature stability throughout the working day. The temperature drop in the evening has the effect of resetting the PCM for the next day or cycle.PCM is trapping heat from room during the day and recrystallization as the temperature drops helps to recharge the PCM
Waxes, not water, for construction Unfortunately water with its temperature transitions at 0C and 100C (32 and 212F) is not suitable for use in construction. In such situations waxes are used, whose melting points can be flexibly adjusted according to the application. BASF’s solution for safely inserting latent heat stores into building materials of all kinds is microencapsulation. Tiny globules of wax 2 to 20 microns in diameter are coated with a layer of extremely hard plastic. These microcapsules are completely sealed, safe to process and free of formaldehyde. In addition, the resultant materials are well suited for further treatment – they are impervious to grinding, drilling, cutting, etc. since their small size makes them virtually indestructible.The encapsulation process also protects the wax in its very pure form, meaning the high heat storage capacity of 110 kJ/kg is permanently guaranteed. Measurements at the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg have confirmed this. In principle it can be manufactured to any switching temperature. BASF’s Micronal® DS 5000 X absorbs the ambient heat energy at around 26C (79F). This temperature has been confirmed by computer simulations to be optimal for passive summer heat reduction in buildings. A material with a switching temperature of 23C (73F) is also available for situations where PCM is to be used as part of a climate control concept.
Fire ReactionAs PCM’s are oil based waxes there are obvious concerns about performance in a fire. Containing the PCM in a metal ceiling tile helps to protect it from flames and also stops some smoke and droplets to escape.When using PCM plasterboards a second layer of plasterboard must be used to give the fire reaction protection. Any cuts into the PCM boards should be sealed with an aluminium tape.CuttingFor the metal ceiling PCM cassettes only full tile modules should be used. The product should not be cut for perimeter cuts or have holes cut into it for services. This will reduce the fire reaction performance. Tiles that have been cut should not be used in the ceiling, they can be recycled easily in main stream recycling streams for steel and plasterboard.Health concernsAs the PCM is microencapsulated there are no concerns about the material leaking out of a product, hence why the product can easily be recycled.InstallationThe PCM cassettes are heavy panels some weigh up to 9Kg each. Care must be taken when moving them around and when installing into the grid system.The cassettes can be installed into a standard suspended ceiling grid, however additional supports may be required. Typically hangers at 1m centres and main runners at 600mm centres.MaintenanceCleaning of the PCM cassettes is the same as for any metal ceiling tile, a damp cloth or a duster in most instances. Mild detergent for stubborn stains.The PCM itself needs no maintained as it is a passive solution and will work continuously for over 30 years.
A standard metal ceiling tile warms up as the temperature of the room increases, this is seen by the green and red colours on the tile on the left.With the PCM insert, as the room temperature increases the heat is pulled through the metal tile and into the PCM.The surface temperature of the PCM tile remains cool. This can be seen by the blue colour of the tile on the right.This continues until the heat capacity of the unit is used up (the wax has changed completely from solid to liquid) After this time the room will continue to heat up if the heating load on the room remains at the same level.The graph shows the difference between a standard ceiling and a PCM ceiling throughout one day.For the standard ceiling the room heats up with the heating load of a typical working office (people, computers, printers, lighting etc) At a certain point the air conditioning is triggered. This then cools the room and shuts off, the room continues to heat and the air conditioning comes on again.This cycle continues until the heat load on the room is removed (the office closes for the night)With the PCM ceiling the room does not overheat, any excess heat above the set point of 24°C is absorbed by the PCM and the air conditioning is not triggered. An even comfortable temperature is maintained and the energy and therefore cost of that energy associated with the air conditioning is saved.In the cool evening in the absence of the heating load the pcm tiles gradually cool, return to solid form and drop the heat energy they have stored back into the room. This means that the room is not too cool first thing in the morning but at a comfortable working temperature and the PCM tiles are reset for another working day.
Some Conclusions When the rooms were sealed during the day and heated, the room containing PCM ceiling tiles was generally 2 degCcooler than the room with normal ceiling tiles. This was the case for heat loads of both 2 and 4kW heat loads per room. When the interior temperatures did not cool below 23degC at night, the room with PCM tiles was still cooler than the room with normal tiles the following day. This suggests that i) the PCM had managed to part freeze even though the temperature hadn’t dropped below 23degC and/or ii) the thermal mass of the PCM tiles provides some buffering, in addition to its latent cooling.
Overhead Air supply with UnductedReturnSystemWith 30% coverage, PCM can be successfully purged with airflow rates typically used with these systems.Purge times are affected by the amount of energy stored in the ceiling (662Wh), purge air temperature and purge air velocity. Lowering the purge temperature from 18ºC to 14ºC decreased the purge time by 3:07 hours.
Sustainability in Ceilings
Using Phase Change Materialsin construction for a moresustainable built environmentPresented byFor further information please contactJeremy Sumeray, Head of Sustainability, Armstrong Building Productsjsumeray@armstrong.com07833 444510
Help you to be better able to understand where andhow Phase Change Materials can be used to create amore energy efficient and comfortable environment
3When to consider Phase Change MaterialsAs part of a low-carbon energy strategy for new build and refurbishmentsImproving thermal comfort for the occupantsOverheating spaces with high demand for air conditioning12639 ampmOUTININIn the hot afternoon, the PCM cassettessuck up the heat and keep the room pleasantly cool.
4PCM needs to be cooled in the evening to re-setBest suited for classrooms, offices, retail, healthcare12639 ampmOUTININIn the evening, the PCM cassettes release the heatand the room is purged ready for the next dayWhen to consider Phase Change Materials
5PCM – thermal mass effectHEAT ENERGYTpLatent HeatSOLIDLIQUIDEquivalent thermal mass3cm plaster, containing 30% PCM14cm concrete18cm bricksPCM’s provide lightweightthermal mass
6PCM Theory – thermal mass effect18202224262830323410/0700:0010/0712:0011/0700:0011/0712:0012/0700:0012/0712:0013/0700:0013/0712:0014/0700:0014/0712:0015/0700:00Without PCMWith PCMTemperature°CRule of thumb:≥3kg/m² floor spaceComparison Air Temperatures [°C]Comfort ZoneStabilizedDate and Time
7BASF MicronalPicture: BASFPicture: BASFMicrocapsules as packagingHuge surface/volume-ratio -> fast heat transferParaffin corePolymer shellPolymer coatingWaxMelting Point:23C / 26C
8• Fire Reaction – Protect PCM fromfire to achieve minimum performance• Cutting – Do not cut PCM cassettes• Health Concerns – As this PCM ismicroencapsulated it causes nohealth concerns. The PCM will notleak out of the product and theplasterboard it is implanted in can berecycled in existing streams.• Installation – Care when handlingand Grid strengthening• Maintenance - Standard cleaningprocedure and no ongoingmaintenance to the PCMHealth and Safety ConsiderationsPCM CassetteAcoustical tile
9PCM cassettes absorbs heat and stabilises room temperature26oC 22oCA cooler surface temp. Also improves the thermal comfort of the space15171921232527299 10 11 12 13 14 15 16 17 18 19 20 21 22 23 2426oC +/- 2.0oC Standard ceiling22oC +/- 1.0oC PCM ceilingHour of the daySurface 1Ch11 [C]
10PCM ceiling tiles with Natural VentilationBelvoir High SchoolPCM ceiling tile
13Case StudyAdd quote hereTest ConditionsStructure: Insulated Thermal Test ChamberHVAC System: 1.Displacement ventilation; 2.Overhead air; 3.Overhead air ductedreturnLocation: BSRIA , Bracknell, UKRoom Size: 16 m2Ceiling Coverage with CoolZone: 0, 30, 57 %Thermal Storage: 0, 662, 1,260WhApplied Cooling Load: 30, 60 W/m2Air Circulation Rate: 2.5, 4.1, 11.1 l/s m2Purge Temperature: 14, 18 0CDisplacement Ventilation System• 662Wh of thermal storage delayed the operation of the air conditioner by 1:20 hours with a 30 W/m²load• 1,260Wh delayed this by 4:27 hours.• The PCM tiles typically reduced temperature variations on the ceiling to +/- 1ºC.
14It is a passive solution, and maintenance freePCM Plays a Role in Supporting High-Performing Real EstateReduces Air Conditioned energy usage by 25 to 50 [%]Offset daytime energy using low energy strategies at night –load shiftingReduces temperature variations, improving thermal comfortImproves energy performance of the building (DECs & CRC)Better lettable rates for low energy buildingsFuture proof - can add tiles at a later dateFlexibleLong term portable assetEasy toincorporateinto existingbuildingsCan bemoved withinthe room ormoved room-to-roomCan locatetiles whereneeded todeal with highheat-load
15SummaryDirect reduction in energy consumptionImproved thermal comfortAvoid cold draughts, air dumping and peak summertimetemperaturesA passive but controllable solution for ventilation and cooling
16ANY QUESTIONS?For further information please contactJeremy Sumeray, Head of Sustainability, Armstrong Building Productsjsumeray@armstrong.com07833 444510