Building insulation

photo Building insulation


Improving hotel building insulation is essential for maintaining indoor temperatures without spending too much for heating. A well insulated building will retain heat longer inside the hotel, and the heating system will not have to operate at the highest level all the time.
Building insulation is an absolute priority for heating savings.
• Thermal insulation of buildings should be considered before replacing heating equipment. It is pointless to invest in a low-energy heating system if heat continues to leak from the hotel building.
• Most heat loss in winter is through the roof and exterior walls. Roof and exterior wall insulation is particularly recommended.
Thermal insulation also reduce the need for air conditioning in the summer.
• Improved thermal insulation is a good way to save on air conditioning, because it blocks solar radiation. But to be truly effective cooling strategies should combine sun protection, ventilation and air conditioning, and the building should have adequate thermal mass (1).
(1) Thermal mass is provided by building materials for walls and other construction elements. Building mass offers inertia to buffer temperature fluctuations. The mass retains heat in winter and coolness in summer, inside the hotel.


Exterior wall insulation techniques
• Exterior walls can be insulated on the outside or on the inside. When feasible outside insulation is preferable, because it adds thermal mass to walls and eliminates thermal bridges or other factors due to poor construction that are the cause of heat loss.
• Inside thermal insulation is generally a dry coating (flexible thermal materials), laminated insulating plaster panels, or fibre insulation materials (rock wool, for instance) nailed into place.
• Outside insulation consists of a layer of insulation applied to the existing wall and covered with a protective finish or decorative sheeting. Dry sheeting offers a wide range of finishes – wood panels, stone, clay bricks, trimming fixtures, aluminium panels.
For hollow walls
• Hollow walls may exist in some countries, i.e. two thicknesses separated by an empty space. The two thicknesses are of standard construction materials (brick or concrete blocks).
Insulation of hollow walls is an economical way to reduce heat loss by convection (up to 35%). A continuous layer of insulation is introduced into the cavity between the two thicknesses. This solution is a first step, with a short payback time.
Thermal bridges in hollow walls can also be treated.

A number of solutions are eligible for energy savings certificates. Among them:
• Attic and roof insulation
• Underfloor insulation
• Outside insulation of exterior walls
• Insulation of roof terraces and
• Inside insulation of sloping roofs
The list of all standard energy-saving operations that are eligible for certificates under the ECS scheme can be found on the French ministry website

Minimum thermal standards for renovation work are stipulated by thermal regulations, by type of wall:
• Exterior walls R ≥ 2,3 m².K/W
• Roof terraces R ≥ 2 m².K/W
• Flooring of underroof spaces R ≥ 4,5 m².K/W
• Sloping roofs > 60° angle R ≥ 2,3 m².K/W
• Sloping roofs < 60• angle R ≥ 4 m².K/W
• Ground floor over outside air space or parking garage R ≥ 2,3 m².K/W
• Ground floor over crawl space or unheated areas R ≥ 2 m².K/W


The best time to insulate a building is when the roof or facade is renovated.
• If your roof or outside walls need work, it's a good time to add insulation. Most labour costs will be already paid, and your only supplemental costs will be for materials and work hours to install the insulation.
A few guidelines must be remembered when a building is insulated.
• It is important to understand how heat and humidity are transferred in the building before deciding to insulate, and a professional must be consulted to obtain the necessary advice. Most walls need to "breathe", and this condition must be respected.
• Thermal bridges must be carefully treated (generally where walls meet the floor, around windows and doors, balconies, etc.).
• When exterior walls are insulated on the inside, care must be taken to avoid condensation in the insulation material.
• When thermal insulation work is done in an existing building, steps must be taken regarding ventilation indoors. A well insulated building will have less natural ventilation, and other ventilation systems will have to be upgraded.


Cost range (costs in France in 2009):
• Inside insulation of exterior walls: approx. €20 - 50/m²
• Outside insulation of exterior walls: approx. €50-80/m²
Approximate payback time:
• Insulation of hollow walls: < 2-6 years
• Exterior wall insulation: < 5-10 years
• Underroof insulation: < 5-7 years
• Underfloor insulation: <5-7 years
It should be noted that costs and payback times are highly dependent on the local setting and the initial situation of the hotel.


In the course of renovation work done to obtain the BBC Renovation low-energy building label, the exterior walls of the Hotel de la Clape (Narbonne Plage) were insulated with 15 cm of polystyrene foam, and windows replaced with double-glazed PVC frame windows, among other work.
A renovation programme at the Hotel des Francs (Soissons, Aisne) ensured performance levels that exceed thermal regulations RT2005 requirements by 40%. This result was achieved in part by work on building insulation:
• exterior wall insulated reinforced with a 150 mm thickness of mineral wool covered by 24 cm thickness of stone facing; insulation under sloping roofs reinforced with 40 cm of mineral wool;
• terraces and ceilings insulated with 120 mm of polyurethane;
• 200 mm of wood fibre insulation under basement flooring and 60 mm of polyurethane under cement slab, thermal breakers created for intermediate floors.
The Ecolodge des Chartrons (Bordeaux) also upgraded its building insulation:
• Roof insulation: 3 layers (each 8 cm thick) of sheep fleece were used to insulate one attic (space not occupied).
Cork panels (10 cm thick), pressed wood fibre board, and FERMACELL panels ( 80% gypsum, 20% wood cellulose) were used to insulate the attic in another building, in an occupied space.
• Insulation of north-facing facade: A mixture of hemp and lime was used for weatherproofing and thermal insulation on the inside of the facade, in one of the rooms. These materials make the walls more weather tight, while letting them breathe, thanks to the lime that is permeable to water vapour. The risk of excess humidity is reduced, and the thermal resistance of the wall preserved.
Cork panels (4 cm thick) were used to insulate the inside of a facade wall in another room.
• Courtyard roof installed The courtyard (27 m²) was covered with a double-glazed structure, to warm the main sitting room and reduce winter heating needs. In summer the windows that give on the courtyards are kept closed, to hold cool air inside.
A 16th-century farm building in the village of Sernhac was rehabilitated with biomass materials to create a B&B that qualifies for the BBC Renovation low-energy building label. Building insulation work consisted of 10 cm of hemp wool to insulate exterior walls, 35 cm of cellulose fleece to insulate the ground floor, and 20 cm of rice straw under the roof.


Cost savings
Energy savings:
• Building insulation retains in heat in winter and coolness in summer, reducing heating and cooling needs.
Potential heating energy savings: between 30 and 50% (with roof and exterior wall insulation).

Comfort improvement
Greater comfort in winter:
• Exterior wall insulation reduces the sensation of "cold walls" in winter, and improves comfort levels for customers.
Increased property values
• In a region where heating needs are high, and given rising fuel prices, a well insulated building is a good investment for the future. Building energy efficiency will be an increasingly valuable asset.
Reduced CO2 emissions
• For a hotel of 1,000 m² that uses 77.5 kWh/m² of natural gas heating annually, and applying emission factors for France, a 35% savings in energy consumption represents:
6.37 t CO2 eq of avoided emissions each year
Emission factors for electricity in France: 84.3 g CO2 / kWh.
Emission factors for natural gas in France: 331 g CO2 / kWh (Source: ADEME).


• Ease of implementation: Difficult (***).
• Best time for implementation: at the time of facade renovation work.
• Relevant initial situation: the hotel building was constructed at a time when insulation standards were low, the insulation has not been upgraded since construction, and the hotel has significant heating needs.