CS13 Tommerupvej 8B. Rehabilitation Workshop in Næstved

Current status: 
Building Owner: 
Næstved Kommune
Consulting EuroPHit Partner: 

Passivhus.dk - Contact person Søren Pedersen

Existing treated floor area (usable floor space): 
244.00 m²
Original situation: 

The building houses rehabilitation workshops, and it is part of a 35.000 m2 complex of buildings, which was erected around 1970 as a centre for mentally disabled.

In spite the rather recent construction, very few relevant drawings of the building and constructions could be retrieved. Informations have instead been gathered on the site.

The buildings were built from prefab concrete elements with 25 mm polystyrene insulation in the outer walls, and typically 100 mm insulation on the roofs. Most buildings have heated basements, or at least crawl spaces, which are cast on site and insulated on the outside with 50 mm hard mineral wool. Windows are wooden with two-layer, air-filled insulating panes.                                                                                     

A pressurization test and thermography showed that the concrete constructions are very air tight. Only leaks are found at the windows and doors.

Ventilation is solely exhaust with no dedicated replacement air openings. One wood workshop has three spot exhausts pulling as much as 700 m3/h, when they are in operation. At these occasions the users of the workshop open a door to the outside.

In some parts of the buildings the users have complained about draught from the windows. With under pressure in the buildings and the leaks mainly located at the windows, this is to be expected.

In neighboring buildings there have been difficulties to even heat them to 20 oC, supposedly because the supply temperature from the district heating plant is being reduced to the lower limit in order to minimize distribution heat losses.

Modernisation proposal: 

We recommended the following solution:

  1. Establish balanced ventilation with heat recovery.
  2. Exchange the original, leaky windows with highly energy efficient windows with low U-value
  3. Mend the remaining, small, leakages
  4. Insulate the basement walls (at that stage we had not realized that they already hat 50 mm mineral wool, which might have changed the conclusion)
  5. Insulate the facades externally
  6. Insulate the roof (tar roofing felt) in 2026, when its service life ends

Steps 1-3 were necessary in order to deal with the immediate complaints about draught.

Planned stages

The building owner also intends with time to insulate the facades. In order to integrate the new windows with the façade insulation in a simple way, the building owner decided to include also the façade insulation (step 5) now. This conditions the insulation of the basement walls first (step 4), as it can hardly be performed later.

The roofing felt is from 2006. Its expected to have a service life span of 20 years, thus the insulation of the roof is postponed.

Performed stages

In the meanwhile the municipality has cut the budget for the project, and only parts of the plan is being carried out:

  • Insulation of all basement walls to 1,87 meters below terrain, which is bottom of the foundation of the crawl space (going deeper, to the bottom of the full basement, is un-proportionally more expensive due to work safety regulations)

Insulation of half the façade and exchange of the corresponding windows (coincidentally not the ones, which caused complaints about draught)

Efficiency improvement: 
PHPP verification sheet before retrofit: 
after retrofit: 
Construction photos (click to view gallery): 
Workshop at Tommerupvej in Næstved. Exchange of windows.
Exchange of windows. Photo: Passivhus.dk
Connection details and thermal performance of the building: 
Other downloadable materials: 
Tommerupvej 8b
4700 Næstved