Q&A Spotlight

Is This Ground-Source Heat Pump Plan Workable?

Posted on February 29, 2016 by Scott Gibson

Jordan Garrow is getting ready to build a new house in New York State, on the cusp between Climate Zones 5 and 6, and he's planning to heat and cool it with a ground-source heat pumpHome heating and cooling system that relies on the mass of the earth as the heat source and heat sink. Temperatures underground are relatively constant. Using a ground-source heat pump, heat from fluid circulated through an underground loop is transferred to and/or from the home through a heat exchanger. The energy performance of ground-source heat pumps is usually better than that of air-source heat pumps; ground-source heat pumps also perform better over a wider range of above-ground temperatures.. His contractor wants to install a horizontal "slinky loop" heat exchangerDevice that transfers heat from one material or medium to another. An air-to-air heat exchanger, or heat-recovery ventilator, transfers heat from one airstream to another. A copper-pipe heat exchanger in a solar water-heater tank transfers heat from the heat-transfer fluid circulating through a solar collector to the potable water in the storage tank., one of several possible options, and Garrow is seeking a second opinion.

A heat load calculation for the house specifies a 4-ton system (one with a capacity of 48,000 BtuBritish thermal unit, the amount of heat required to raise one pound of water (about a pint) one degree Fahrenheit in temperature—about the heat content of one wooden kitchen match. One Btu is equivalent to 0.293 watt-hours or 1,055 joules. /hour), but the contractor wants the heat exchange loops designed as if they were serving a 6-ton system.

Solar Now or Later?

Posted on February 15, 2016 by Scott Gibson

Prices for photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. (PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow.) systems have been dropping steadily, making the investment in residential-sized arrays more appealing than ever. Lower prices and a decision in Congress to extend the federal investment tax credit means that ever larger systems are within reach of more homeowners.

But what about homeowners whose construction budgets strictly limit the size of the PV system they can realistically afford? They are people like James Timmerberg, who is building an all-electric house in Ohio and would like to invest in solar — if it makes economic sense.

Foundation Plan for a Snowy Climate

Posted on January 18, 2016 by Scott Gibson

Nathan Scaglione's central New York State building site gets plenty of snow and cold weather during the winter, and that's proving to be a sticking point in his plans for a new house.

He'd prefer a slab-on-grade foundation rather than a basement, even though a full basement would be a more typical choice in this part of the country. The foundation would consist of concrete-block stem walls extending to a footing below frost line. Exterior walls would be framed on top of the block walls, roughly 24 inches above grade. Inside the block walls, Scaglione will pour a concrete slab floor.

Solar Panels or Exterior Foam?

Posted on January 4, 2016 by Scott Gibson

Apollo S has been making steady energy upgrades to his pre-war Cape Cod style house in Massachusetts. He's replaced a steam heating system with a heat pumpHeating and cooling system in which specialized refrigerant fluid in a sealed system is alternately evaporated and condensed, changing its state from liquid to vapor by altering its pressure; this phase change allows heat to be transferred into or out of the house. See air-source heat pump and ground-source heat pump., and with help from the state's energy efficiency program, he air-sealed and insulated his attic with cellulose.

As a result, his $250-a-month energy bills are one-quarter what they used to be, and Apollo now has his eye on the next round of upgrades.

Choosing the Right Water-Resistive Barrier

Posted on December 21, 2015 by Scott Gibson

Yes, James Timmerberg's new house will have a water-resistive barrierSometimes also called the weather-resistive barrier, this layer of any wall assembly is the material interior to the wall cladding that forms a secondary drainage plane for liquid water that makes it past the cladding. This layer can be building paper, housewrap, or even a fluid-applied material. (WRB) on the exterior walls.

What To Do With All That Recessed Lighting?

Posted on December 7, 2015 by Scott Gibson

Justin Brown has moved into a house with lots of recessed lighting fixtures, including 10 six-inch Prescolite non-airtight fixtures on the second floor ceiling, and another 11 mounted in cathedral ceilings. He may have plenty of light in those rooms, but he's more concerned about all the air that's leaking into the attic and rafter bays and the heat loss that goes along with it.

Radon Mitigation in a Leaky House

Posted on November 23, 2015 by Scott Gibson

RadonColorless, odorless, short-lived radioactive gas that can seep into homes and result in lung cancer risk. Radon and its decay products emit cancer-causing alpha, beta, and gamma particles. mitigation in new construction is now routine when testing finds that concentrations of this odorless, cancer-causing gas exceed government-recommended levels. Writing from southeastern Wisconsin, Andrew S. has a slightly different problem: How to control radon levels when you live in a leaky log home built in the 19th century.

Designing a Low-Slope Roof That Works

Posted on November 9, 2015 by Scott Gibson

If only Kevin Hoene's choices for a new roof boiled down to a choice between an EPDM membrane and metal, his life would probably seem a whole lot simpler.

But Hoene, building a new home in Illinois and on the boundary between Climate Zones 4 and 5, will soon be weighing the pros and cons not only of different roof coverings, but also of what type of insulation to use, whether it should go above or below the roof sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. , and whether the roof should be vented or unvented. In other words, nothing seems off the table.

The Best Way to Insulate a Foundation

Posted on October 26, 2015 by Scott Gibson

Nethaniel Ealy, a builder in Idaho who's about to pour a concrete basement foundation, is trying to come up with insulation and waterproofing details that will be effective and within the budget.

The current plan is to place 2 inches of extruded polystyrene (XPSExtruded polystyrene. Highly insulating, water-resistant rigid foam insulation that is widely used above and below grade, such as on exterior walls and underneath concrete floor slabs. In North America, XPS is made with ozone-depleting HCFC-142b. XPS has higher density and R-value and lower vapor permeability than EPS rigid insulation.) on the outside of the foundation walls. At some point in the future, the homeowners would place another 2 inches of foam on the inside of the foundation walls between 2x2 studs, and then apply drywall over the studs.

Detailing Exterior Walls in Minnesota

Posted on October 12, 2015 by Scott Gibson

In Minnesota, Jeff Fredrickson is planning a new house, and his research has included lots of reading on the design and construction of exterior walls. His goals are twofold: a wall that will stay mold-free for decades, and one that is "somewhat energy efficient."

Starting at the inside, the wall would go like this: drywall, a polyethylene vapor barrier, JM Spider insulation in 2x6 stud walls, 1/2-inch plywood sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. , a water-resistive barrierSometimes also called the weather-resistive barrier, this layer of any wall assembly is the material interior to the wall cladding that forms a secondary drainage plane for liquid water that makes it past the cladding. This layer can be building paper, housewrap, or even a fluid-applied material. (Benjamin Obdyke HydroGap), fiber cement and stone veneer claddingMaterials used on the roof and walls to enclose a house, providing protection against weather. .

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