The principle of a modern and economical system consist in dual-zone circuit arrangement of forced air distribution in a family house:

• primary circuit provides circulation warm-air heating together with controlled fresh air ratio and heat recovery with air supply to every room via floor grilles
• secondary circuit provides separate air exhaust of bathrooms, kitchens, possibly slosets with heat recovery

Ducts of both air-handling circuits are connected to a common DUPLEX RB, RC, RD air-handling unit, designed and patented by ATREA s. r. o.


Legenda

c2	circulating and fresh air into rooms
e1ZR	outside air supplied through a ground exchanger
i1	exhaust air from bathroom and kitchen
c1	circulating air from rooms into AHU
i2	outlet of exhaust air after heat recovery
RC	DUPLEX RD heating unit ventilator
IZT	integrated IZT heat storage tank (optional)
ZR	ground exchanger (optional)
S	water solar collectors (optional)

Family house


Apartment building

Ventilating, heating and cooling modes

The DUPLEX units serve the year-round requirements of the house microclima according to a selected operating mode on a CP controller:

• equal-pressure ventilation with heat recovery
• warm-air circulation heating and equal-pressure ventilation with heat recovery
• warm-air circulation heating (with occasional ventilation)
• negative-pressure ventilation of bathrooms with intake of preheated air
• positive-pressure summer ventilation (mainly night precooling) possibly cooling with air supply throuhg a ground exchanger

APARTMENT BUILDING	DUPLEX RC; RB	FAMILY HOUSE
1. Equal-pressure ventilation   (nv = 0,3 to 0,5 h-1; nc = 0) Year-round - equal-pressure ventilation with adjustable air volume flow (80 to 150 m3/h), with heat recovery or using a by-pass.

APARTMENT BUILDING	DUPLEX RC; RB	FAMILY HOUSE
2. Circulation and ventilation   (nv = 0,3 to 0,5 h-1; nc = 0,5 až 1,5 h-1) Heating season - warm-air circulating heating and equal-pressure ventilation with heat recovery.

APARTMENT BUILDING	DUPLEX RC; RB	FAMILY HOUSE
3. Circulation heating with occasional ventilation   (nv = 0; nc = 0,5 to 1,5 h-1) Heating season - basic circulating heating mode. Ventilating mode "2" is switched on via an impuls from a bathroom or a kitchen, or in periods using a timer.

APARTMENT BUILDING	DUPLEX RC; RB	FAMILY HOUSE
4. Negative-pressure ventilation   (nv = 0,3 to 0,5 h-1; nc = 0) Summer or off-season period - negative-pressure air exhaust of bathrooms with air supply via the AHU.

APARTMENT BUILDING	DUPLEX RC; RB	FAMILY HOUSE
5. Positive-pressure ventilation - cooling   (nv = 0,5 to 2,0 h-1; nc = 0) Summer - positive-pressure room ventilation using outside air supply (possibly via a ground exchanger with cooling).. Air exhaust via open windows.

c1	Inlet of circulating air from rooms into the unit
c2	Outlet of circulating air from the unit into rooms
e1	Inlet of fresh outside air
e2	Outlet of fresh air from the unit into rooms
i1	Inlet of exhaust (stale) air from bathroom into the unit
i2	Outlet of exhaust air from the unit

Technical solutions and functions of the air-handling system

• circulation and fresh air distribution to rooms is standardly distributed via individual flat (200 x 50 mm) ducts made of galvanized sheets laid in thermally insulated floor layer. It is recommended that supply air outlets with control be located under windows to avoid cold draft, as well as covering by furniture. This system also avoids acoustical interferens between different rooms.
• circulation air returns from individual rooms via a slot under doors into a corridor where it leaves the space via a wall grille under ceiling into vertical ducts and back into the unit.
• the circulation and fresh air are then filtered in the unit by a G4 class filter with efficiency up to 94%, heated in a hot-water heating coil, and then are forced by a centrifugal low-speed fan (with variable volume flow) through sound attenuators back to rooms.
• in the unit a fresh air drawn via facade louvers or a ground exchanger is mixed and filterd with the circulated air in a set ratio, and then preheated in a heat recovery core with efficiency up to 90 %.
• stale air from bathrooms and water vapor from kitchens are constantly (possibly occasionally) exhausted via controlled valves and round duct with diameter of 100 to 160 mm and forced into the unit. The ductwork is installed in false ceiling. The exhaust air gives its heat to the fresh air in a heat recovery core. Cooled exhaust air is forced by a smaller exhaust fan through facade louvers out off the building.
• exhaust hoods above stoves are circulating with odour-absorbing carbon filters. They have adjustable volume flow of 150 to 450 m³/h.
• manual dampers (250 x 100 mm) in floor outlets contol the air volume flow, as well as the air temperature in individual rooms
• hot-water or electric heating elements (ladders), possibly floor heating (heating panels) are used for temperature increase in bathrooms
• The compact DUPLEX RD, RC, RB unit is placed on request in any of closets or small rooms or just next to a wall or under a ceiling (DUPLEX RB only).
• It is recommended for low-energy family houses that an space airchange of n = 0,3 h^-1be met. That ensures during a continuous operation the building's comfort indoor air quality at approx. 25 m³/h of fresh air per person (Pettenkofer criterion).
• The flat floor duct is designed for the max. air volume flow of 80 m³/h (at max. airflow of 2,0 m/s). Eachduct then brings 600 W of heating capacity to rooms at the max. temperature drop of the circulated air of 45/20 °C.
• During duct and shaft design comply to ČSN 730872 - prevention against spread of fire in buildings via air-handling system.

Energy sources and systems

ATREA created complete versions of energy systems suitable for low-energy and pasive family houses and swimming pools.
Based on a particular house and investor's requirements the DUPLEX units can be installed with all heat sources (electric boilers, gas boilers, heat pumps, solar systems etc.). Integrated heat storage tanks (IZT) can be added to the system in some reasonable cases..
For more information see the respective design specification materials..

Examples

Integrated IZT heat storage tank for solar heating of hot serwice water (HSW) and space heating (SH) supplement with built-in upper element for flow heating of HSW, lower element of a solar exchanger for connection of solar collectors, and electric elements for heating season and summer. The IZT heat storage tank can be hooked up to a biomass-burning boiler or a heat pump.

Condensing natural gas boiler, possibly an electric boiler or a heat pump with a built-in or separate HSW heater. Standard gas-burning boilers already have a built-in capacity controller based on water temperature ensuring modulating capacity control.

Air-to-water” heat pump with bivalent electric supply, integrated IZT 615 heat storage tank for space and HSW heating.

Sources and appliances

Ground exchanger

The ground register (ZR) serves to natural air conditioning (cooling) of buildings in summer and for ventilation air preheat in winter. It also protects the heat recovery core against freezing.
The ground exchanger comprises of an underground duct of length of 20 to 25 man inlet shaft and a shaft cover with a filter above the ground. The supply air is heated in the ground exchanger during winter from -15 °C to + 2 - + 5 °C, and is cooled during summer from + 32 °C to +19 - + 22 °C.
The ventilation air enters the DUPLEX unit during off season through outdoor louvers located on building facade and a standard "T" fitting with dampers and an actuator. Switching between air intake from louvers or the ground exchanger is controlled automatically based on an outdoor temperature sensor located on noth side of the building.

Principles of a ground exchanger design

• duct Ø200 mm laid min. 1,8 m in ground with 1 - 2 % slope for good condensate drainage. The covering soil should not include sand, gravel nor other insulating material
• duct length 20 to 25 m, straight run without bends no grater than 30° with respect to cleaning
• material of drainage pipe of PVC, (PP, PE) Ø200 mm smooth,connected by rings
• recommended soil: moist, clay; gravel and sand etc. is not recommended
• intake shaft of the ground exchanger made of polypropylene, dia. Ø800 mm