While it perhaps isn't as sexy as picking out cabinets, flooring or plumbing fixtures, the energy measures taken in a building are critical. Perhaps our grandchildren will have the opportunity to choose between a plethora of recycled metal plumbing fixtures, ready to assemble cabinetry made from reclaimed materials, and the like. But, we're stuck in the "green" dark ages where significant focus is placed squarely on energy (which IS very important, of course). So...with that...let's pull up our sleeves and talk about the heating system.
This house will have a condensing boiler "combi" system. That sounds simple enough but is actually pretty sophisticated equipment. While our heating systems are not even close to approaching the complexity of your car...we've come a long way. When the fuel in your boiler is burned, the chemical reaction produces water vapor (which requires energy to form). It used to be that this water vapor would be exhausted into your chimney...dumping energy out the chimney. Now, we take those warm exhaust gases and allow them to decrease in temperature, which causes the water vapor to condense into liquid water ... in turn releasing energy. It's a relatively small amount of energy that is captured ... but this gets your boiler from 85% to 90% efficiency. That's the "condensing" part.
Now, the "combi" part means that we are combining the boiler with the water heater. Rather than having a combustion system in the water tank and a second (typcially more efficient) one in the boiler ... wouldn't it be smart to have just one combustion system? So...there are two main ways that a combi system can be made. One is to circulate water through the combustion system "on demand", meaning that if you open your hot water spout, your heating unit kicks on and heats the amount of water you need when you need it. This can require a really big combustion system ... but you don't have to store a tank of water. On-demand systems are an efficient choice for small and/or intermittent uses (like vacation homes) or may be a good choice for homes with limited space. The other option is to store a tank of water, and periodically circulate the water through the heating system burner in order to keep it hot until you are ready to use it. This system is quite similar to a conventional water tank except that the tank does not have it's own combustion system, but borrows the combustion system from the space heating system. That's what we picked out...the tank option is more efficient than the tankless option when you use hot water frequently.
Still with me? Ok, one of the last (and I think coolest) tricks is that the latest and greatest heating systems now measure the outdoor temperature to adjust the water flow rate through the house. That way, when it is warmer outside you dump less heat into the house than when it is colder outside. Remember a time (usually in what we call the "shoulder season" during Fall and Spring) when you were a little cold, the heating system would turn on, and you would roast...then open your windows? This was because the heating system could not regulate the amount of heat added to the house ... only whether or not to add heat. Heating systems were sized to make sure you got enough heat in the coldest part of winter ... and the rest of the time, you could always open your windows! The amount of fossil fuels literally thrown out the window over the past 100 years is astonishing. Arguably, adding variable speed pumps to heating systems is one of the greatest energy savings measures made to heating systems over the past few decades.
Now for distribution. There are two main ways that energy generated in the combustion reaction is distributed within the home nowadays....with liquid water or air. We chose liquid water becuase it holds more energy per mass, has a lower profile (small baseboard heaters rather than larger openings for air ducts), and is considered to be more efficient (although this depends on quite a lot of things ... but generally, air ducts are leaky sieves and a huge pain to keep tight over the years). A heat exchanger (think of the radiator in your car) sits inside the heating system. When the fuel is burned, it transfers heat energy to the liquid water, which is circulated through baseboard radiators throughout the house.
We've also elected for 4 thermal zones within the house, one for each bedroom and one for the living room/kitchen/family room/dining room "communal" spaces. 4 zones are way overkill but this is such a nice feature in a home. The homeowners will be able to set different temperatures in these spaces depending upon how they choose to use the rooms (office, playroom, sleeping room, ...).
So, as you can see, we really invested in making sure we had a robust, reliable and incredibly efficient heating system. It's nice to know that someone will thank us for that!
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