Client:
Wohnungsgenossenschaft WOGE Nordstadt eG
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Schneiderberg, Hannover
Description
Before the modernization
The WOGE Nordstadt housing corporation purchased the building in 2005 with the intention of doing comprehensive renovation work on it. The need for action was great: bathrooms on the stairwell landings, an apartment divided by the stairwell, electric night-storage heaters in living areas, electrically-powered direct heating units in the bathrooms even remnants of wartime damage and an old bakery oven filling one room all severely affected overall living comfort in the building.
The modernization
The goal of the renovation was to create simple, solidly equipped apartments with affordable rental prices. In order to minimize heat loss, the exterior walls were fitted with a mineral-wool composite thermal insulation system, Passivhaus windows were installed, and the roof was insulated with cellulose as part of the roof truss restoration work. Interior insulation on the top floor prevents heat from escaping into the neighbors' unheated attics. Due to spatial differences, the basement ceiling insulation was completed partly from above and partly from below as part of a new floor construction. Consistent use of Passivhaus components made it possible to reduce the building's heating energy needs to 21 kWh/(m2a). The renovations helped to make heating the living spaces much simpler: heat is distributed over the ventilation system using a re-heater. Only the bathrooms have separate heating elements. Pellet heating is used to generate hot water as well as the residual heat needed for room heating; the pellets and pellet stove are located in the basement.
Parties involved
Planning:
bauart Architekten,
Dipl.-Ing.-Architects Friedhelm Birth and Detlef Christ
Building data
Building type:
Apartment complex
Location:
Hannover-Nordstadt
Year of construction:
circa 1900
Modernization:
2006
Residential units:
10
Heated living space:
637 m²
Subsidies:
dena model project, urban construction subsidies provided by the state of Lower Saxony and the City of Hannover, BAFA, proKlima
Initial condition
Exterior Walls:
Plastered solid-brick walls, HTC ?1.2–2.9 W/(m2K)
Windows:
Wooden or plastic windows with heat-insulating glazing, some with single-layer glazing; HTC ? 2.5 W/(m2K)
Roof:
No significant thermal insulation; some lightweight wood-fiber construction panels inside; plastered; HTC ?1.4 W/(m2K)
Basement ceiling:
Concrete ceiling with steel supports; HTC =1.4 W/(m2K)
Ventilation:
Ventilation through windows as well as through joints and cracks typically found in old buildings
Heating:
Night storage heaters
Modernization in detail
Exterior walls:
Mineral wool composite thermal insulation system measuring up to 20 cm thick; quality: 0.036 W/(mK); HTC = 0.16 W/(m2K)
Windows:
New Passivhaus windows with heat-insulating triple glazing; wooden frames; glass spacers made of plastic
Roof:
New roof truss construction with wooden lightweight beams and 35 – 42 cm cellulose insulation between roof rafters; quality: 0.040 W/(mK); HTC = 0.11 W/(m2K)
Basement ceiling:
Up to 20 cm thermal insulation installed on either the top or the underside; quality: 0.035 W/(mK), HTC = 0.17 W/(m2K)
Ventilation:
Comfort-ventilation systems with heat recovery and re-heating functions in each apartment
Heating:
New central 25-kW wooden pellet boiler with 500 liter buffer storage and 300 liter drinking water storage capacities; heat distribution via supply air and bathroom heating elements
Measured values
AIRTIGHTNESS:
n50= 0.57 h-1
Calculated values
Calculation method: Passivhaus planning package; Initial values: Hannover building typology
HEATING ENERGY NEEDS:
BEFORE
170 kWh/(m²a)
AFTER
21 kWh/(m²a)
SAVINGS
88 %
TOTAL ENERGY NEEDS FOR HEATING,AIR CONDITIONING,DHW,ELECTRICITY:
BEFORE
Electricity
188 kWh/(m²a)
Gas
26 kWh/(m²a)
AFTER
Pellets
48 kWh/(m²a)
Electricity
20 kWh/(m²a)
PRIMARY ENERGY NEEDS FOR HEATING,AIR CONDITIONING,DHW,ELECTRICITY:
BEFORE
519 kWh/(m²a)
AFTER
59 kWh/(m²a)
SAVINGS
89 %
CO2-EMISSIONS FOR HEATING,AIR CONDITIONING,DHW,ELECTRICITY:
BEFORE
125 kg/(m²a)
AFTER
15 kg/(m²a)
SAVINGS
88 %
