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AHT Inc. Plumbing & Heating specializes in comprehensive system design, installation and service of energy-saving plumbing and heating systems for residential and commercial clients. Our plumbing and heating services are focused on alternative-energy technologies that utilize solar and solid fuel sources for sustainable on-grid or off-grid plumbing and heating solutions.


Green Woodlands alternative energy home in Lyme, New Hampshire


Featured Project

Green Woodlands Alternative Energy Home
Green Woodlands is a very unique project that was designed to meet the highest standards of environmental stewardship and built to be a model for living off-grid through the utilization of alternative energy sources. The purpose of the project is to provide an example of the best environmental design and construction technologies appropriate to the Northern New England region. AHT Inc. Plumbing & Heating was contracted to design and install all the plumbing, hydronic heating and hot water systems for the Green Woodlands project.

Project Goals
Green Woodlands meets the highest standards of environmental stewardship and promotes a model for education and research by utilizing the best environmental design and construction technologies available today

LEED Certification
Green Woodlands has been accepted in the Leadership in Energy Environmental Design (LEED) for Homes Demonstration Pilot, a program developed by the US Green Building Council.


The team from AHT INC. installs a Radiant Floor Heating System at Green Woodlands


Plumbing & Hydronic Heating Systems
Energy for the hydronic heating systems at Green Woodlands is provided through a combination of a wood-fired boiler with propane backup. When required, electrical input to the systems may be obtained from either hydroelectric and/or solar photovoltaic for powering the backup condensing gas boiler if necessary. All these energy sources then contribute to a thermal storage tank where heat is stored and released at even temperature through radiant floor heating circuits. The sealed and well-insulated building envelope allows for the project to achieve low energy input goals with fresh air supplied by an energy recovery ventilator. Water conservation is demonstrated with the use of composting toilets and recycled grey water with a cultivated milkweed plot to allow for water reuse.

Hydronic Heating Systems

• Tarm solo wood-fired boiler
• Viessmann Vitodens WB624 Combi propane boiler and on-demand hot water heater as system backup
• 780 gallon non-pressurized heat storage tank for radiant floor heat and hot water systems

Plumbing Systems
• Composting flush toilets
• Grey water system with a cultivated milkweed plot for water reuse
• No PVC pipe is used in plumbing systems (ABS & Cast Iron only)
• High water-usage efficiency is achieved through piping design & low flow fixtures
• No solder fittings are used on piping (PEX tubing and Pro-press copper fittings)
• All piping for heating or domestic water is insulated to prevent condensation
• Hot water heat recovery systems is installed on drains

Radiant Floor Hot Water Heating System
The main floor and second floor of the building have PEX tubing embedded in a thin layer of concrete that is covered by hardwood flooring. Hot water is pumped through the tubing, which evenly heats the flooring and then radiates up throughout the building. The radiant floor heating system uses a 780-gallon super-insulated hot water storage tank as its heat source from a Tarm solo wood-fired boiler.

Wood-fired Boiler
Burning wood efficiently allows Green Woodlands to use a resource that is renewable, readily available and does not contribute a considerable amount of pollution to the atmosphere. In an environmentally sound manner, the wood-fired boiler uses cordwood to heat the 700-gallon super-insulated water storage tank. Operating at an extremely high temperature (1800 degrees), it quickly and efficiently burns the cordwood (and wood gases) to capture and distribute heat. The hot water is then used for both the radiant floor heating system and domestic hot water for showers and washing.

Propane Boiler and Hot Water System
Green Woodlands uses a Viessmann combination propane boiler and on-demand hot water system to act as a backup system. This high-efficiency addition to the heating system also functions as a control and monitoring device for the entire heating system. The Viessmann Vitodens WB624 Combi boiler operates at an AFUE efficiency of up to 98%. In the event that the clients are not at home to put wood into the Tarm Wood-fired Boiler, then the high-efficiency propane boiler will kick in at a predetermined temperature.

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