It’s the Envelope, Stupid!

We keep lamenting the amounts of energy used by buildings, but it’s like the proverbial weather in New England: nobody does anything about it. The quote, by the way, may go back not to Mark Twain, but to Charles Dudley Warner who was an editor at the Hartford Courant.

Be that as it may, buildings are supposed to protect us against the elements, and they are generally fairly good about keeping you dry, but not not so good at maintaining comfort at a reasonable cost, as we are dealing with changing energy costs. We should remember the old history that New York City’s infamous steam radiators were designed during the Spanish Flu of 1918 for the express purpose of overheating the room so you could have fresh air and heat at the same time. At that time coal was the fuel and nobody thought about cost or emissions.

But that was then, and this is now, and the cost of energy is no longer an afterthought. In the real world with existing construction, we often encounter situations where you cannot retrofit effective insulation, and also, in applications such as frame construction you often have a huge problem with thermal bridging, as the studs may make up 17% of the wall and provide no insulation at all. But, there are better solutions. For thermal performance, we really need to look at three areas: The walls, the windows and the roof. And instead of merely slowing down the heat loss or heat gain, how about blocking it altogether?

The Walls

We’ve all gotten used to the idea of insulation in walls and ceilings, which means insulation between the studs, and we’ve also learned something about vapor barriers, for any moisture in the insulation compromises the performance, but there are clear limitations to the ability to control the performance satisfactorily outside the lab. Particularly the vapor barrier is often a problem spot.

What if there were a barrier that could reject the heat entirely, and thus keep it inside in summer and outside in winter, instead of letting it escape. We represent a ceramic coating, Super Therm, that does exactly that. It is part of a whole family of coatings that address a variety of problems, but for our discussion of reducing the thermal load of the building this feature of not letting the heat (& moisture) escape is the key. Plus, given it is only a 10 mil coating, it can be applied to perimeter walls and top floor ceilings anywhere. We need to adjust our thinking away from insulation towards rejection of the heat, and the measure is emissivity, the respective tests are (ASTM C1363 and ASTM C1371).

We should also take into account that the advertised R-values of insulation materials do not work outside the laboratory. Air leakage and condensiation (moisture barrier!) are probably the biggest factors that compromise the performance. The coating is continuous and can last 20 years.

The Windows

We all like light, and sometime ventilation, and we end up with the biggest thermal holes in our building envelope, which we do not want to get rid of. There is an answer and it is called the InFlector Window Insulator. Used as either fixed (reversible) screens, roller blinds or vertical blinds, it hangs behind the window and creates a thermal barrier, while the material itself has a reflective side and a dark side, to bounce back or attract the light and heat from the sun. It is see-through, but effectively cuts out solar glare. The material further also screens out UV-radiation. Installed, it solves the problems of reducing heat conductivity of the windows, and reduces air infiltration, taken together, these features typically produce a reduction in the thermal load of buildings between 20-40%. Of course mileage may vary depending on local conditions such as the relative size of the windows compared to the rest of the building envelope, and the orientation of the building, including shade from adjacent buildings, etc. Again high emissivity – reflecting heat and light – is the key to the performance of the reflective side of InFlector(TM).

There is also a slight difference depending on what type glazing is in the property. For single glazing the reduction in heat loss is around 85% and for super-fancy gas-filled double glazing the reduction is still 75%. Conversely in winter, with the dark side facing out, a 4′ x 4′ area of window on the sunny side generates as much heat in the room as a 600 Watt electrical heater.

The Roof

The final most obvious feature in the energy-loss picture of a property is undoubtedly the roof, because heat rises. And in the summer roof with low emissivity attract too much solar heat. With Super Therm we can coat most roofs, and/or the ceilings on the top floor can be coated on the inside. This alone can prevent typically 10-20% of heat loss through buildings.

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1 thought on “It’s the Envelope, Stupid!”

  1. We should remember that as we change the thermal dynamics of the building, heating system boiler response needs will change. The conversion from outdoor reset to indoor feedback control is essential to adapt for the most efficient boiler operation. ” Let’s tame those puppies to real needs, at best fuel use.” The savings will reduce chimney waste and fuel bills.

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