Can We Design Buildings for Heat and Cooling that Mimic the Human Body

Lucas Hamilton

Lucas Hamilton is Manager, Building Science Applications for CertainTeed Corporation

I spend lots of time thinking about buildings. Sad; I know. Lately I have been wondering how we wound up in such a confusing state. It’s like looking under your car hood. Have you looked under your hood lately? It looks like a building design. Who in their right mind would have started out to design such a complicated mess? No wonder we need so many building scientists and we pay a hundred bucks an hour to get our cars fixed. Can we step back for a minute?

Thermal comfort in the built environment needn’t be so complicated. If we could start from scratch and try to make buildings comfortable based upon our own organic experience, what would we do? I live in Philadelphia.  If I go outside in the winter and try to passively stay comfortable – passively meaning to not use any outside energy sources – I would use lots of layers of clothing, would zip up tight and cover my skin.

Coincidentally that is what we require in our cold climate building codes.  Lots of layers of clothing means R-value. When you wear lots of layers of clothing you are trapping gas inside layers.  The gas is the insulation – gas gives you resistance to conductive energy heat flow – that’s R-value.  So when you are wearing lots of layers you are wearing R-value. When we say zip up – that’s getting air tight. We finally woke up and added that one to the cold and mixed climate codes as well.

The problem comes in the summertime. To stay cool, you would take off those layers, wear light colors and try to get air flow around you.  You would wear airy fabrics to release as much heat from your body as possible and light colors which don’t get hot in the sun. If you were stuck wearing lots of layers and were zipped up tight, you would have to blow cold fresh air into that outfit to stay comfortable. Our goal should be not to do that. Remember, passive technologies rule and active technologies cost $$$.

We need to find ways to help a building be warm in the winter and stay cool to begin with in the summer. I am looking for changes to our practices that will enable us to do to buildings what we do to ourselves. How would you build your building differently?

If you can’t strip off all the layers of clothing the very least you will do is unzip so can we figure out a way to unzip our buildings? I know we want to be air tight in the winter but can we figure out a way to use air to remove surface heat in the summer? I think ventilated claddings may be one answer.

Can you think of some others? To go back to the car analogy, let’s stop bolting more stuff onto the internal combustion engine to make it more efficient and drop in an electric motor. It needn’t be so complicated.

Simple Changes Could Help Consumers Save on HVAC

Lucas Hamilton

Lucas Hamilton is Manager, Building Science Applications for CertainTeed Corporation

California has again pushed their energy bar higher.  One of the things that I love about California’s energy program is that they are now requiring an independent evaluation and commissioning beyond the air conditioning contractor of the sizing and installation of air conditioning systems. 

Recently, I participated in a workshop with a Philadelphia-based builder. He is a very professional, conscientious builder who stays in touch with building science and education. He brought his mechanical contractor to the workshop and we had a chance to talk about the way homes are built and particularly the mechanical systems. 

Here is the situation:

  • There are still ‘rules of thumb’ being applied to the sizing of mechanical systems in our homes. 
  • Manufacturers make changes to equipment to help those ‘rules of thumb’ meet the requirements, especially regarding motors and equipment that can tune itself to the needs of the house. 

What we really need are systems that are designed and installed to the actual house. 

We can’t expect equipment to be continuously updated or modified to make up for our lack of willingness to do a simple calculation as to what the house really needs. It’s not just about the tonnage of air conditioning and the size of the heating units.  It is mostly about the delivery – the physics of the delivery – of that comfort.

When someone tells me something regarding heating or cooling that just isn’t sitting well and I need a gut check, my gut actually lives out in Missouri and his name is Eric Kjelshus. He is a Missouri Mechanical Contractor with his own company, Eric Kjelshus Energy. He is a smart, thorough, well studied mechanical contractor who cares about this stuff far beyond anyone else I have come across.

It seems like many of the builders I have spoken with have been spending a lot of effort (effort = $$) after the sale trying to make the homes they have constructed meet the comfort expectations of the owners. This leads me to wonder if there are things we consistently get wrong with regard to how we deliver comfort. Time for another gut check!

Here is what Eric taught me:

We under return air in our homes.  Very few people consistently measure static pressures in the HVAC system to find out if it is balanced. If they did they would see that the system is not returning the same volume of air it is supplying. When we under return, we force the system to pull make-up air from outside the home.  Air conditioning is more efficient when the air is dry. For most of us residing east of the Rocky Mountains, the return air in our homes is both cooler and dryer than the air outside during our cooling periods. Pulling unconditioned and uncontrolled air from outside the home into the system is a big efficiency penalty and it’s one we pay for over and over again. Why not simply return the correct volume of conditioned air back to the unit? Not only is this an elegant, passive solution to the problem –  it comes with a much lower up front cost than high tech solutions.

So hats off to California for requiring that trained professionals check these systems to ensure they are properly sized and installed. We as consumers can get much better value out of systems that are less sophisticated but are sized and built right.