Re: Phase Change Materials - anyone used this?2
Jul 21, 2017 2:09 am
I'm no expert on this. But I would say, just be careful adding thermal mass to your second story. As hot air rises, in summer second stories can become hot in the day. Thermal mass will inhibit cooling in the evening, keeping bedrooms hot on summer nights. Of course this isn't always the case, & is dependant on your climate, the design of your home, & even the temperature at which your chosen PCM changes phases.
Re: Phase Change Materials - anyone used this?3
Jul 21, 2017 3:52 pm
You're right ddarroch. We are in Sydney and we would use the recommended BioPCM version for the optimal temp range (can't remember which off the top of my head). House is designed for cross ventilation and openings at highest points to release rising hot air.
Re: Phase Change Materials - anyone used this?4
Jul 24, 2017 1:23 pm
I ran some calculations and it seems it cheaper or comparable cost to go double brick, instead of BioPCM, but in addition you are also getting an improved acoustics, structural stability and termite protection.
Thermal mass makes sense for the first storey only, though.
As already mentioned above, for the bedrooms you don't need it - you would need quick cooling/heating, so I would invest into heavy insulation and improved acoustics instead.
For example, a very good alternative is to consider the use of a lightweight timber construction with rendered XPS panels for the second storey.
Re: Phase Change Materials - anyone used this?5
Jul 26, 2017 11:17 pm
Thanks for your reply alexp79. Interesting about the cost - I had intended to go reverse brick veneer for the ground floor, but it turns out it would cost around $60k to use brick and $20k only for PCM. RBV on the upper floor didn't even get a look in, considering the cost of steel reinforcement support beams etc!
I'll have to do more research on using PCM on the second floor. BioPCM (the supplier) recommends using the stuff in ceilings and the roof to absorb the rising heat. I get what you and ddarroch are saying about releasing the heat when the air temp goes down though. I'm still going to try and find someone who's actually used pcm in a residential build, because both arguments make sense and now I'm conflicted!
Re: Phase Change Materials - anyone used this?6
Jul 26, 2017 11:28 pm
You can read about Thermal Mass here:
You should be very careful about second floor thermal mass.
Strange that your bricks cost so much. My calculation is that you spend $0.75 on brick costs and $1.5 per brick on labour. There are 50 bricks per sq m, so the wall costs you $112.5, let's say $120 per sq m.
Also, you might only need bricks in north facing areas, so should not be costing you more than 20K.
Re: Phase Change Materials - anyone used this?7
Jul 27, 2017 12:08 am
I read through that entire site when I first started to look at building, it's been incredibly helpful!
PCM cost is around $115m2, and relatively low installation cost since it comes in sheets. I'm thinking the RBV cost I was quoted also includes attaching the gyprock as nails or whatever need to go into brick rather than timber studs?
Good point too, about maybe needing bricks only on north facing walls!
Re: Phase Change Materials - anyone used this?8
Jul 27, 2017 12:14 am
I would say you need bricks on the walls opposite and around north facing walls, north facing walls themselves will be having a lot of glazing, so having bricks on them won't have much of an effect.
You might also decide to keep one or two brick walls as a feature too.
My understanding that you would need to have multiple layers of BioPCM for the right effect.
Another solution is Knauf PCM gyprock boards. It is also quite expensive, but you don't need to do anything other then regular plastering to install those to your ceilings.
Re: Phase Change Materials - anyone used this?9
Jul 27, 2017 9:31 am
I'll be contacting the BioPCM guys to speak to them directly. There's a couple of videos on their website that explained things nicely and answered quite a few of my questions.
I believe having multiple layers increases the "thermal inertia" of the building so it's more effective in extended periods of extreme temps. Not sure if it's needed for Sydney climate though - so eg in summer I would think as long as the night temps go below 18c this allows the pcm to refreeze and reset for the next day. In peak summer might need to use air conditioner a bit to refreeze. That's something I'll have to ask them.
I didn't think knauf boards were available anymore, something to do with the smell of the paraffin as it changed phase?
Re: Phase Change Materials - anyone used this?10
Jul 31, 2017 8:11 am
Personally I see the material as just another way of selling/promoting insulation and a claim to provide a desirable solution at a cost.
Any/ all insulation is a resistance to loss or gain
below is a copy and paste off an online site
[size=100]The purpose of which is to limit heat loss or gain.[/size]
In domestic and general buildings, during winter months, to limit heat loss through the ceiling and walls where the manner of construction consists of a thin membrane material such as plasterboard as a lining.
Its corresponding performance during the summer months comes with a plus minus effect, in that the greater the amount of insulation, the greater the storage potential, therefore the longer the building will take to purge itself of the heat load during the evening cycle.
The interior of the house is less resistant to ambient change.
Various entities including govt. based organisations will attempt to suggest that insulation will provide all the necessary comfort levels desirable but disappear into the wilderness when asked to show their rationale, or attempt to change the narrative.
The reality is that there is no advantage without a corresponding disadvantage and anyone advising differently should be questioned as to rationale.
Bigger is not Better!
In most conditions, the use of an insulative medium above r3.0 is not warranted and even then should be used in a manner so saturation does not occur, and any high heat load absorbed can be dissipated quickly and efficiently.
A decision should never be made until full awareness has been acquired.
Unfortunately there are those that think that when a word ends in ‘ion’, one is a substitute for the other.
A dangerous presumption!
Insulation, Ventilation, Air conditioning have totally separate areas of function and one does not replace, and or, is a substitute for, the other. Just as do the tyres, steering wheel and brakes in a car.
In simple terms:
Insulation – is like putting an on overcoat, to prevent heat loss or gain
Ventilation – is like breathing
Air Conditioning -cooling -a cost based climate system controlling living conditions reliant on consumption of electrical energy with or without water.
Putting on an overcoat is not going to make you breathe any better,
and the air conditioner is not going to improve the quality of air.
Conversely, breathing well is not going to make you any warmer, but it will contribute to your remaining cooler, and is guaranteed to keeping you healthier.
Use the right product for the right reasons and avoid trying to demean the validity of the product, or approach, on the basis of financial outlay because in the end you are the one that is ultimately going to wear the outcome
As with anything, correct understanding always produces the best decisions.
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