PASSIVE HOUSE –ZERO ENERGY BUILDINGS
Now you also save on CO2 pollution by lowering your heating/cooling cost by more than half.
MHE-ACC has one important property, what non of the traditional building materials have, and this is ISOTROPIE, which means, the material has in all Directions the same properties, which is the basis for airtight and buildings with no cold bridges.
Our cell structure is so unique, that our building air pockets give the same thermal properties in all directions. We all know that air is a good insulator, Therefore MHE-AAC is the only choice to build the a PASSIVE HOUSE or a
ZERO ENERGY HOME
Thermal performance of AAC wall, Floor and roof system provides an innovative combination of excellent thermal conductivity, Thermal mass and low air infiltration.
Let’s talk about equivalent R-value.
An 8” AAC block with 3/8 Stucco and 3/16 plaster can be compared to a wood farming structure with a framing 16” o.c , 5/8” stucco, ½” plywood and a R20.4 fiberglass insulation finished with ½ drywall and to an 8” CMU wall with 5/8 stucco R-8.6 Rigid Insulation, wood furring and also finished with a 1/2 “Drywall. All those said, for those calculations the diffused radiation was used only. So when we apply the direct radiation (sun) then AAC would even perform better. We also need to look at the EPI (Energy Performance Index) to meet the thermal efficiency. We compared an 8” AAC home with an R-11 wood frame home and 8” CMU home with R-5 insulation. We all used the same windows. The EPI index cannot exceed the value of 100, AAC received a value of 84.4 the wood frame house received a value 91.85 and the CMU house received 89.71 this shows that AAC is 10% more energy efficient than wood house and 5% more energy efficient than CMU house.
However to comply with the residential energy efficiency code we rotated the building in 45 degree increments to re examine the efficiency. The resulting EPI values indicated that a house built with AAC complies with the code regardless of the building orientation while the other wall systems would fail
.It is important to remember that thermal performance of any building material is the result of several factors and may not be assumed either effective or ineffective on the basis of any one of those factors.
Basically let’s look at 3 definitions, Thermal conductivity “K” which measures the conductivity of the building material. The major factors is the density, AAC with 32 pcf “pound per cubic foot” of design density weight, performs 10 times better than 150 pcf concrete and as half as good as polystyrene insulation board. The R- Value however depends on the material Thickness and the density. The R-value shows the resistance of a material to conduct or allow heat flow. Here again an 32 pcf AAC material, 8” thick, performs again 10 times better than a 150 pcf concrete wall 8” thick. But their 8” AAC wall performs up to 70% as good as 3 ½ batt insulation.
Now let’s look at the heat transmission coefficient U-value, which is defined as how much heat transmits through 1 sqft of a building envelope in 1 hour. Those results are matching the same outcome. Like the R-value but as soon as we look at the specific heat, which shows how much heat is required to raise 1 lbs of material by 1 degree Fahrenheit it shows clearly that it takes 20% more heat to raise the temperature of an AAC building than of an concrete building and it takes 35% more heat to heat up an AAC building then an 3 ½ batted insulated wood frame house. Lets look at the heat capacity, which will shows us how much heat can be stored we call it “thermal mass”, so we want to see in the winter time how much of heated air our building can store. Here we measure it again in BTU/ sqft per degree F.
An 8” AAC wall can store the produced warm air in our buildings 4 times better than an 8” 150 pcf concrete wall.
Lets look again at the thermal mass benefit concept, “steady R-value” for example our values, where we assume that the temperature on both sides of the wall is constant for a period of time which is very unlikely, actual conditions show a temperature change on the outside during the day, but inside we do not want to have any changes. AAC reduces the temperature transfer, So that a 30degree F exterior temperature change will not affect the interior temperature. This is based due to the shown excellent heat capacity of AAC which causes a reversal in the direction of heat transfer, back to the outside within a 24 hour period.
Subsequently, the total heat gain through the AAC wall system is significantly less than Low thermal mass wall systems such as a framed wall. In this case, the combination of the heat capacity and the excellent thermal resistance exceeds the performance of a high “Steady State “R-value. This dynamic process is known as the “thermal mass benefit” or “Mass-Enhanced “R-value.
Again as we seen it takes 0.25 BTU to heat 1 lbs of AAC by 1 degree F “specific heat”
So by having 32pcf it would require 5.4 BTU to heat an 8”AAC wall 1 degree F.
In a test, we measured the temperature fluctuation over a 24 hour period to a west wall painted black to increase surface temperature , the outside wall temperature fluctuated by 126 Degrees F and the inside temperature remained at a pleasant 68degrees F.
Here again the “time lag” with the heat capacity gives us such excellent results.
Not to forget is the air tightness, AAC has a 1/8” thin set which creates the air tightness but CMU has a ¼ thick mortar joint and air can easily escape there.
Also more dense materials are decreasing the effective R-values.
So let’s look at the wall system and not at the separate single materials only.
Also, water content, condensation is a factor of the effective insulation value 5% TO 10% water content in any material can decrease the effective insulation value by more than 15%.
MHE-International your partner in regards PASSIVE HOUSE and ZERO ENERGY BUILDINGSEmail: info@mhe-international.com
or Call: 1.888.847.1077
