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Heating and Cooling

Equipment choice. People with custom homes appear to have fallen in love with radiant heating. Before you go this route in your SIP home, consider your broader requirements. Since your SIP home will need mechanical ventilation, the fresh air introduced to the home should be distributed, not just dumped in one location. That means you will need some ductwork for distributing the air. If so, why install two distribution systems--one for radiant heat, another for fresh air? This can add several thousand dollars. Instead, get double duty by using your fresh-air ductwork for heating and cooling as well.

Smarter equipment sizing. Consider these two key points about equipment sizing. First, heating and cooling loads in SIP homes should be lower than that found in today's average new homes. And second, studies show that heating and cooling equipment installed in most new homes today is typically oversized by 40% to 100% above and beyond the recommended "25% fudge factor." If you're planning to build a SIP home with good low-e windows and tight construction, do yourself a favor and have your HVAC contractor both calculate the projected loads and then show and explain to you those calculations. Bottom line: you should be able to recoup some of the higher costs for your SIPs construction by installing smaller heating and cooling equipment-perhaps only half the size of the typical unit for that size home. While the savings for installing a smaller furnace are modest-typically $75 to $150-the savings on heat pumps and air conditioners can be considerable, from $500 on up.

Smarter ductwork layout. Here's some heresy: even in a cold climate, if you build a tight SIP home with good low-e windows, you don't need to play the traditional game of distributing heated and/or cooled air to the perimeter walls. You just need to get the air into the room in question. Sealing the ductwork is twice as important as delivering heat to the outside edge of the perimeter. So run your ductwork to interior walls, typically right beside the doorway, and seal your ductwork either with mastic (never tape) or the new Aeroseal system (if available in your market area).

Sealed combustion appliances. If you only get one thing right in your SIP homes, make it combustion safety. With natural gas or propane appliances, the only way to guarantee this is by installing sealed-combustion models: furnaces, water heaters, gas fireplaces. This adds at least $500, 250 and $150 to the price of each appliance, respectively. You should consider this one of the cheapest insurance policies on the market today.

The next-best strategy is very difficult: install non-sealed appliances in a space (basement, garage, crawl space) that is isolated from the home, and in which any ductwork is airtight in order to not create air pressure problems within the combustion zone.

Two-for-one option. Compared to the recipe above, you can save several hundred dollars by installing a "combo heater." Select a seal-combustion water heater that gets hooked up, via a water-to-air heat exchanger, with an air handler unit. When the house calls for heat, house air is heated as it is blown past the heat exchanger and through your standard ductwork. This system has been used in hundreds of thousands of multi-family dwellings in mild climates, but is also quite appropriate for well-insulated SIP houses in cold climates.

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