Browse Forums Eco Living 1 Aug 30, 2011 10:13 pm Hi there, I live in Perth, Western Australia. We have a temperate environment with hot dry summers and mild winters. We're planning to build a two storey Reverse Brick Veneer house. We're planning to have a suspended subfloor on the ground level. This is because a) the block has a slope 2) is located next to a 100 year old flood plain 3) we want to have a large amount of rainwater bladder tanks located under the house to supply the household water with mains as back-up. We will also have a greywater system for the garden and solar power panels on the roof. Because we will have two suspended slabs the cost is prolific and have been looking at alternative options. So far we've looked at a) Hebel powerfloor b) InsulFloor c) Particle board with insulation within the truss I'm confused about Thermal Mass vs Insulation in our scenario. My understanding is as follows (please correct if I am wrong): Thermal Mass: A concrete slab has a greater thermal mass. Being a suspended slab will have less thermal mass than a slab on the ground. Thermal mass acts as a 'storage bank' of energy/heat. It is recommended to have dark stone or polished concrete so it absorbs/stores heat/energy from the sun during the day and assists in maintaining internal room temperature whilst outside temperature may cool down. We're planning on having timber floors and carpet - what affect does this have on the benefits of thermal mass? Does timber and carpet affect it negatively and therefore the cost of suspended concrete slab isn't worth it? Insulation: My understanding is that insulation helps prevent the loss of heat through floors/walls/roof. So thermal mass in a concrete slab helps 'contribute' to a comfortable internal temperature whereas insulation helps 'prevent' heat loss? So am I correct to think that if you don't have good thermal mass on the floor, but have a good amount of insulation you can still achieve a comfortable internal temperature by gas heating certain rooms you use (eg. lounge with doors closed) and electric blankets in bedroom? Or do I have this completely wrong? Sorry I'm confused! What role does thermal mass and insulation play in Summer? Heat is of more concern where I live. Thanks for any help! Re: Thermal Mass vs Insulation 2Aug 31, 2011 7:35 am Hi, Firstly, about floor coverings on concrete, yes, timber flooring because they lay battens down to put the flooring on, acts as a barrier for transmission of heat. Carpet to a lesser extent does as well but the less dense the carpet you choose, the better. Saying that though, if the exterior side is well insulated, thermal mass can still work through floor coverings. As for insulation vs thermal mass, thermal mass helps regulate temperature whereas insulation resists changes in temperature. They're both good but if you're building reverse veneer, that could probably be enough thermal mass and I would be more concerned about insulation, especially if you're having your subfloor fully open. Powerfloor with some good soffit insulation would be my personal choice. Hope that helps. Newtown rebuild: https://forum.homeone.com.au/viewtopic.php?f=53&t=48977 Re: Thermal Mass vs Insulation 3Aug 31, 2011 11:59 am In the situation where you have a slab on the ground the soil acts as both thermal mass and like insulation. It acts like insulation because the temperature underground is constantly around 18-20 degrees C so there is minimal heat loss directly downwards, only at the edges of the slab. The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Thermal Mass vs Insulation 4Aug 31, 2011 1:15 pm Think about insulating your slab edge. 1 metre of 25 mm foam either beside the footings or along the ground if you are then covering it. Your understanding of thermal mass and insulation is good. If you don't heat or cool your house, the comfort of you house will be the multiplication of thermal mass and insulalation. It's very hard to double your insualtion (basically need to double the thickness of the insulation), but you can easily increase your thermal mass by over 20 times by using brick and/or concrete on the inside of your house. This is why full brick houses (that are kept closed during the day and ventilated at night) are comfortable in summer, withiout any air-conditioning. Demolition August 2009, Construction Started September 2009, Completed December 2010 Re: Thermal Mass vs Insulation 6Sep 05, 2011 10:02 am The effectiveness of thermal mass is dependant on your climate. They work best in temepratures with a a high diurnaal range ie. a large difference between day and night temperatures. If your climate does not have cool nights, the mass will not release heat, and will just keep heating the house, making it not so pleasant. If you do want thermal mass it does not have to be in the slab. You can also acheive it by (clay) brick or concrete walls. You can even have one internal brick wall that receives sun from north facing window as your thermal mass. It is not really an 'either/ or' with thermal mass and insulation, they have different purposes. If you are more concerned with keeping your house cool than heating it, work with insulation. Reflective insulation keeps out heat. If you are allowed, roof your house with colorbonf 'Coolmax' Have a product like foilboard under the ceiling and around the walls, before your cladding is put on. If your floor is suspended (and not a slab) have underfloor insulation Then, to keep your cool air in: Have the highest rating bulk insulation batts in your ceiling and walls that you can. But other things to consider would be: The orientation of the house on the block Have no windows (or if you have to few and small) on the west side Ensure you North windows have shading from summer sun (deciduous trees are good) Try to stop heat hitting the house in the first place with design of eaves location of carports and outbuildings garden design Design your house so there are windows opposite each other (with no internal walls interupting) and windows that open for maximum air (eg casement) so at night you can get good crossflow to cool the house down. There's lots of stuff you can do to have a regulated temperature even if you can't have the slab Re: Thermal Mass vs Insulation 7Sep 07, 2011 2:03 pm Would it be possible to build it with on ground slabs then build in a void and floating / raised floor? With sufficient space of around 0.7 of a meter + you could simply build a decked floor above the slab. This would be good in some ways because you can store water in the slab, insulate the floor and use more efficient sub floor heating from solar based, bio based energy systems. Re: Thermal Mass vs Insulation 8Sep 20, 2011 7:50 pm A few points. 1. You have lots of thermal mass inside the house given you have RBV, so you can live without the slab. You normally want 6m2 of thermal mass exposed to the sun for every 1m2 of north facing windows. One of the major reasons you want a slab is because the sun can hit the slab in winter via north windows and absorb the heat energy, to be released over the next 12 hours. To ensure you get best benefit you need to analyse how the sun is going to hit the thermal mass. 2. I would recommend hebel powerfloor. It is a great product, and has some thermal mass as well insulative qualities. To increase its thermal mass you could tile over it with bluestone or similar. Together with the screed, you then have closer to suspended slab and alot cheaper. 3. Why do you want bladder tanks? They are expensive on a per litre basis. You would be better off $ wise with a 20,000 concrete tank buried under the ground (esp if doing cut and fill). Re: Thermal Mass vs Insulation 9Sep 20, 2011 11:02 pm I am not overly convinced that a slab in contact with the ground is necessarily a good thing. It greatly depends on the average soil temperature in your location (which varies with climate and water content). It can result in significant loss of heat through the floor despite the increased capacity to store it. In a temperate climate, mass should be well insulated. As you mention it acts as a thermal battery. Insulation prevents the 'leak'. A suspended floor with underfloor insulation may act more effectively at conserving the energy. RBV works well in this regard because it is 'off the ground' In winter, ensure the mass is heated directly by radiant solar heat via north facing windows. This builds up a store of heat that maintains stable temperature at night and on sunless winter days. In summer, ensure the mass is well shaded by eaves/solar pergolas so it doesn't become an uncomfortable heat bank at night. Perth has a fairly mild climate so that RBV with standard insulation levels will most likely maintain very comfortable temperature throughout the year. A cool temperate/alpine climate with less sunny days and cold nights will require a higher proportion of insulation to mass (no sun = no energy to heat the mass). Hey guys building a new place through a volume builder and just wondering if i should complain to the site supervisor as we just had plasterboard installed. Looks like… 0 11279 1000000% definitely add insulation. I have in my home and it makes a big difference minimising sound transfer. Insulation is pretty cheap and definitely worth it 2 6209 |