integrated space and water heaters

Hot water and air-space heating are usually provided by different systems. But they can be integrated in new homes or in a big remodel... A combined system can provide energy savings over non-integrated systems.

The parts of the integrated system

Integrated (combined) space and water heating systems provide both… space heating and hot water to households. The design and the components of these systems may vary and can be based on boilers (the most common), condensing water heaters, heat pumps, or furnaces (the less common)...

Obviously, these systems are hydronic: they provide hot water for space heating through hot water radiators or radiant heating floors (and for showers and other hot water domestic uses).

Fuels

These integrated systems can make use of very different fuels or energy sources.

Boiler-based systems can use gas, but also electricity, oil and pellets… Solar energy can also be associated to boilers and gas and other fueled water heaters. Modern heat pump based systems (using electricity) can also be used...

Advantages of integrated systems

An integrated system with a good design may offer lower energy costs (EPA estimates them around 25% over other systems) and also lower installation costs. Integrated systems contain fewer parts to service, allowing a less expensive installation and an easier maintenance.

Costs & Disadvantages

Despite possible savings over non-integrated systems, a typical system like a gas-boiled system with water-heater-radiators is a costly one (rarely above the $3,000), with relatively high running costs.

Strategies involving zone heating, solar water heaters or solar passive heating should be considered prior to integrated central systems.

New buildings and large remodeling projects

Integrated systems should be designed in the framework of a new construction or a large remodeling project.

As part of a central heating system, combined systems are best installed during the construction phase and rarely as a retrofit.

The boiler based systems

Many integrated water heater-space heating systems use boilers. Boilers provide hot water to the radiant heating loops (for space heating through hot water radiators or radiant heating floors) and also to a water storage tank (for showers and other hot water domestic uses).

Integrated space hot water heating Image on left (from the Department of Energy): the hot water heating part of an integrated system.

Design

The design of integrated systems is very important to get lower costs and energy-efficiency. The location of the parts of the system is particularly important. The boiler, the storage tank and other parts of the system should be located as close to each other as possible.

The boiler should be conveniently sized to supply the home needs. Details like programmable thermostats and automatic valves in the baseboard heaters are crucial to energy efficiency.

See: Space Heating with Radiators and Radiant heating

A all-In-One water heater-Space Heating Unit

It's possible to have an high-efficiency device providing both domestic hot water and space heating, based on a powerful water heater or some device very similar to it.

Typically the system uses a modulating condensing gas appliance, and an hydronic loop. These solutions are rather common in Europe, but not so much in USA. The HTP Versa-Hydro model is one of the first all-in-one devices to integrate a high-efficiency water heater with a space heating element for the American market.

In some cases, the system is designed just to provide the hot water needs of the bathroom, kitchen or other specific room (the water heater is often located near one of these rooms) and the space heating of part (just part) of the house.

Installation

Combined systems demand an adequate sizing and relatively sophisticated controls. Installation requires a licensed HVAC contractor and often a licensed plumber.

Prefer UL (Underwriter's Laboratories) certified systems. In USA, for natural gas-fired systems, consider also the American Gas Association certification.