air-source heat pump

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How Does a Heat Pump Get Heat From Cold Air?

The physics of heat pumps isn’t really that difficult to understand

Posted on Dec 6 2017 by Allison A. Bailes III, PhD
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Cold weather is coming back to Atlanta this week, so let’s talk about heat. An increasingly popular way to heat buildings these days is with heat pumps, even in cold climates. But how do they work?


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Image Credits:

  1. Energy Vanguard

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Should We Promote Heat Pumps to Save Energy?

Replacing electric resistance heat with heat pumps could trim the nation's consumption of electricity by 2% — but in very cold states, gas furnaces still use less energy

Posted on Jun 2 2016 by Steven Nadel

Heat pumps are going through a period of innovation. Ductless heat pumps are more available; cold climate heat pumps have been developed; higher minimum efficiency standards for heat pumps have been established by the U.S. government; and gas-fired heat pumps have been developed.


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Image Credits:

  1. BlueberarsLair / CC BY-ND 2.0 / Flickr

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Ductless Minisplits May Not Be As Efficient As We Thought

New England researchers find that minisplits have lower air flow rates and lower COPs than expected

Posted on Oct 16 2015 by Martin Holladay
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A recent monitoring study of ductless minisplits installed in seven New England homes found that these heating appliances had lower airflow rates and lower coefficients of performance (COPs) than expected. The average COP of these air-source heat pumps ranged from 1.1 at the house with the least-efficient minisplit to 2.3 at the house with the most-efficient minisplit.

The results of the study raise at least as many questions as they answer. Perhaps the most useful outcome of the study is that it sets up a framework for recommendations that could enhance minisplit efficiency.


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Image Credits:

  1. Photo of dog on floor: Peter Talmage; all other images: Consortium of Advanced Residential Buildings

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Do Ductless Minisplits Work With Every Floor Plan?

Or do these air-source heat pumps only make sense for open floor plans with few rooms that are closed off from the rest of the house?

Posted on Aug 31 2015 by Scott Gibson

Clay Whitenack, planning a new home in central Kentucky, had assumed that 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. would be a "no-brainer" for heating and cooling. Then he began reading about minisplit air-source heat pumps, and suddenly the situation didn't seem so simple.

He's intrigued with the possibilities for minisplits, but he's not certain he'll have a floor plan that would be compatible with this type of system, he writes in Q&A post at Green Building Advisor.


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A Canadian Couple Needs Help Choosing a Heating System

Weighing cost, comfort, and reliability for a heating system that has to work while its owners are away for months at a time

Posted on Jul 6 2015 by Scott Gibson

John Ball faces the usual questions as he decides on a heating system for his new home: What system will deliver the best results at the lowest price? What will keep Ball and his wife comfortable in their Canadian locale in Climate Zone 7?

But there's something else that Ball has to consider: Their new retirement home will be empty during the winter when they're in Florida escaping the snow and the cold. As they get older, and health care becomes more expensive, they expect to be returning to Canada on a year-round basis.


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Image Credits:

  1. Wikimedia Commons

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How To Buy a Ductless Minisplit

This cheat sheet is intended for designers and builders who are confused by available equipment options

Posted on Jun 19 2015 by Martin Holladay
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Green builders usually specify high-performance windows and above-code levels of insulation, while striving to reduce air leaks in their homes. As a result of these efforts, most green homes have relatively low heating and cooling loads.


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Image Credits:

  1. Alex Wilson

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Minisplit Heat Pumps and Blizzards

Outdoor units that are mounted near grade can get buried by snow

Posted on Feb 19 2015 by Marc Rosenbaum

A blizzard (a severe snowstorm and sustained winds of over 35 mph) is a challenging weather condition for a minisplit 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.. Recall how an air-source heat pumpHeat pump that relies on outside air as the heat source and heat sink; not as effective in cold climates as ground-source heat pumps. works: the outdoor unit has a compressor and a fan that blows air across a coil with refrigerant. In heating mode, the coil is colder than the outdoor air. As air is drawn through the coil, it gives up heat to the coil and leaves the other side colder.


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Image Credits:

  1. All images: Marc Rosenbaum

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Designing an HVAC System for a Cold Climate

An owner-builder weighs two options for heating with an air-source heat pump

Posted on Jan 19 2015 by Scott Gibson

Randy Bunney is building a new house in a challenging environment — north central Minnesota, where overnight temperatures plunge well below zero and heating-degree days over the last three years have averaged more than 8,600 annually.

The high-performance, passive-solar home will be a relatively small 1,100-square feet with two bedrooms, an open living-kitchen-dining area, 1 1/2 baths, a mudroom and a mechanical room. Bunney is planning on exterior walls insulated to R-40, the roof to R-60, and "near airtight" construction.


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Image Credits:

  1. Scott Gibson

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An Energy Upgrade On a Budget

A homeowner has to choose among recommendations from an energy audit: More insulation, new windows, or an air-source heat pump?

Posted on Nov 10 2014 by Scott Gibson

Christian Rodriguez has taken an important first step in improving the energy efficiency and comfort of his 1880s home by arranging for an energy auditEnergy audit that also includes inspections and tests to assess moisture flow, combustion safety, thermal comfort, indoor air quality, and durability.. With the results in hand, his first step was to air-seal the attic and add 20 inches of cellulose insulationThermal insulation made from recycled newspaper or other wastepaper; often treated with borates for fire and insect protection..

"This made quite a difference both in comfort and heating bills," he writes in a Q&A post at Green Building Advisor. Now comes a difficult decision: what to do next.


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Image Credits:

  1. Christian Rodriguez

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Looking for the Best Minisplit Option

Planning a new house, two GBA readers decide that conventional ductless minisplit installations are unappealing, and suspect that filter changes would be a hassle

Posted on Jun 30 2014 by Scott Gibson

Ductless minisplit heat pumps have gotten many favorable reviews at Green Building Advisor, but Roy Goodwin sums up a concern that's popped up more than once: Despite their virtuoso heating and cooling performance, they're a little on the homely side.


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Image Credits:

  1. Image #1: Peter Yost minisplit
  2. Image #2: Fujitsu
  3. Image #3: Peter Talmage

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