Planning and building a new house is the time to make sure energy efficiency is ‘baked in’ right from the start. It’s a lot cheaper to build an efficient house at the beginning than to try to improve it later. Any investments in efficiency will pay returns in the form of lower energy costs for as long as you own your home. It will also be healthier and more comfortable, and have a higher resale value. A home that doesn’t lose its heat quickly can take advantage of a much smaller and less expensive heating system.
The Alaska Housing Building Energy Efficiency Standard (BEES) was established by the State of Alaska to promote the construction of energy efficient buildings. It sets building energy use standards for thermal resistance, air leakage, moisture protection, and ventilation. Your house should receive a minimum of a 5-star rating. Confirm that your designer & builder are familiar with those standards and can explain the methods they plan to use to achieve them.
A heat pump is one of the most efficient systems available to heat your home. Planning for a heat pump from the start will result in a cheaper installation and better performing system.
Whole-House Heat Pump Options
There are two general categories of heat pumps systems to choose from – ductless and hydronic.
Hydronic Heating Systems
Hydronic systems produce warm water that can then be circulated through your house to heat the floors, radiators, air handlers, and even your domestic hot water. These can be very efficient and effective systems, especially if you plan for them at the start. They offer the flexibility to precisely target where in your house the heat is delivered to. The ability to heat your domestic hot water (usually the second largest consumer of energy in your house) with your heat pump is a significant advantage over ductless systems.
Hydronic systems can be ground-source heat pumps (GSHP) or air-to-water heat pumps (AWHP). Ground source systems extract heat from the earth by running fluid through coils or wells buried in the ground. The heat that’s extracted from the ground is then ‘concentrated’ using a compressor and refrigerant system, and warm water is delivered the house. The advantage of a GSHP is that it can operate efficiently even at very low outside temperatures because it’s extracting its heat from the relatively warm, constant temperature earth.
A few disadvantages of a GSHP are: 1) it entails a significant amount of heavy equipment to bury the earth-loop tubing, either in trenches or in vertical wells and it may require a significant amount of land on the building lot; 2) the initial installation cost can be quite high, easily exceeding $20,000; 3) due to its complexity it will likely require specialty engineers and installers; and 4) residential GSHP systems are relatively uncommon in Juneau so local expertise and support may be limited.
An air-to-water heat pump extracts its heat from the ambient outdoor air and delivers it to the house as warm water. It has the same advantages as a GSHP regarding how heat is distributed throughout the house. It also avoids the significant expense and complexity of the earth-loop system installation. Because it must extract heat from the ambient air, its efficiency decreases as outside temperatures decrease. There are not many suppliers of AWHP systems in the United States, so selection and support may be limited.
Ductless Heating Systems
Ductless heat pumps (DHP) are by far the most common systems in Juneau. These systems extract heat from the outside ambient air and distribute it indoors using a variety of different blower systems. In large open spaces a wall or floor mounted ‘mini-split’ head is the most common and effective system. Smaller rooms often use air ducts to distribute warm air to multiple rooms from a single ducted indoor unit. A house can utilize a combination of these systems. Another strategy is to deploy a hybrid of heating systems, such as mini-splits in the main areas of the house and electric resistance heaters in the smaller, less frequently used areas. This can often be the lowest cost approach while still retaining most of the energy savings benefits of the heat pump, because it’s still providing the bulk of the heat called for by the house. Planning for system component placements, especially for ducted systems, is easy to do early in the process – it can be much more difficult after the fact.
- Heat pumps, regardless of variety, require a substantial amount of electricity. This should be planned for in advance by your electrical contractor. Outdoor units have specific requirements for where they’re located, both for protection from the elements and for proximity to the indoor units. Electrical service to those locations should be planned for early.
- Thought should be given to where thermostats will be located. You will want the thermostats located in the rooms that are being directly heated by the heat pump, but not in a location directly in the path of the heat pump’s outlet. Control wires should be run prior to the installation of the sheetrock.