Many custom home builders are asked to build homes with design features or specific upgrades the builder wouldn't recommend but ultimately feel obligated to build for their client anyway. When it comes to energy efficiency upgrades cost effectiveness, upkeep, and replacement costs should always be considered. In many cases a customer's money is more appropriately allocated to upgrades in the building shell, which lowers the overall energy needed to heat and cool and offers greater comfort to the occupants. These are the 3 most common upgrades custom clients seem to be enamored by that I believe are a misuse of funds.
- Ground Source Heat Pumps: Commonly (inaccurately) referred to as "geothermal" heat pumps. Yes, there is something enticing about a system that exchanges heat energy with the natural ground temp of 50 degrees F ultra efficiently but at what cost? Digging the trenches for these systems and burying the network of ground loops requires working with a large surface area or horizontally digging straight down which can be very expensive. Expect a total system cost of $30K or more for one of these. What if one of those ground loops ever leaks? What if the site contains lots of bedrock? The cost just went up.
In the fairly temperate climate of the Willamette Valley air to air heat pumps now offer similar energy efficiency at a fraction of the price. If a component ever breaks downs it's a lot easier to work on and there are many more HVAC contractors skilled on air to air systems than ground source systems. In colder climates (Central OR for example) or larger existing homes with a bigger heating load an argument could be made for ground source heat pumps.
- Radiant Floor Heat: Who doesn't like the idea of a warm floor under your bare feet in the winter time? The problem with this idea is that newly constructed, well insulated and air sealed homes have such a low heating load, and radiant floor provide such a large heating surface area, that that dream is never fully realized. For the floor to feel warm it needs to be so warm that it would easily over heat the space. The other large drawback is that this methodology of distributing heat energy offers no ability to effectively cool a space in the summer time. Running cold liquids through the lines creates condensation that is both harmful to the flooring and dangerous for homeowners who could easily slip and fall.
With a ductless system or forced air system you can typically heat and cool a home much faster. If the ducted system includes a ducts inside distribution strategy similar energy efficiencies can also be gained at a fraction of the price.
- Spray Foam Insulation: Customers are attracted to the idea of expanding foam filling every little gap, crack, and void in a complicated assembly full of wiring, plumbing, and more, as well as the inherent air sealing capabilities in one convenient product. The elephant in the room is that most spray foams are petroleum products, contain harmful blowing agents, and have Global Warming Potentials so high that it's often impossible to overcome their embodied energy through a lifetime of operational energy savings. Slight changes in air temperatures, surface temperatures, humidity, and more can affect the integrity of the spray foam mix that happens during the install. Without near perfect conditions flawed installs are common and can result in poor mixing, fires, and fish like smells in the home while the product off gases.
Dense pack cellulose insulation and blown in blanket fiberglass insulation both offer the same ability to fill every little gap, crack, and void in a complicated assembly. Using an air sealing checklist like the Thermal Enclosure Checklist, builders that use tapes, caulks, and point of use canned spray foam products offer the ability to air seal homes just as well, if not better, and many prominent building scientists believe for longer periods of time as the wood building structure moves over time. These products have much lower embodied energy and Global Warming Potentials so they tend to payback themselves over the lifetime of home energy use.
