Insulation rules when renovating
As soon as you renew a roof, facade, or floor, you enter the legal domain of the Bbl. That is the successor to the Building Decree and governs minimum technical requirements for buildings under the Environment Act. One of those requirements relates to insulation: every building component you replace or substantially renew must meet a minimum thermal resistance (the Rc value). This article explains how the rules work, what they mean for roofs, facades, and floors, and how Tekenpunt records the insulation composition in the construction drawing so your application is immediately correct.
The Bbl sets insulation requirements per building component you renew: if you replace the roof, facade or floor, that component must meet the minimum Rc value (thermal resistance). Unchanged components may retain their existing level, known as the legally acquired level. The renovation requirement is lower than the new-build requirement but is binding; the exact Rc values are tightened periodically and can be found in the current text of the Bbl or via the IPLO.
How the Bbl looks at insulation for renovation
The Bbl distinguishes between new construction and renovation. For new construction, the strictest requirements apply: the entire building must comply with the current energy performance requirements (BENG). Renovation works differently. The entire building does not have to comply with the new-build requirement all at once. Instead, an obligation applies per building element: if you replace a part of the building envelope, that element must after replacement comply with the insulation requirement that the Bbl sets for that situation.
The renovation requirement is generally lower than the new-build requirement, but it is still binding. Anyone who replaces a roof, re-clads a facade or renews a floor must demonstrate that the new building element insulates sufficiently. The thermal resistance is expressed in the Rc value (in m2·K/W): the higher, the better the insulation.
The legally acquired level For existing, unaltered building elements the so-called legally acquired level applies. This means: a wall you do not touch during the renovation does not need to comply with the new insulation requirement. You may retain the insulation value the building element already had, even if that value does not meet the current requirement. But as soon as you renew or replace that building element, that protection lapses and the current Bbl requirements apply to the altered component.
This distinction is crucial: it forces you to check per building element whether it is being modified. If you do not do this and skip the insulation requirement, the structure will not comply with the Bbl after completion. That can cause problems during an inspection or when selling the property.
Roof insulation: when the requirement applies and what changes
Replacing a roof is one of the most common situations where the Bbl insulation requirement comes into play. Think of replacing roofing on a flat roof, fitting a pitched roof with new boarding, or a complete roof structure being rebuilt as part of a renovation.
When does it count as 'renewal'? Not every roofing activity triggers the insulation requirement. Minor maintenance (replacing a few roof tiles, sealing a leak) is different from a major roof renewal. As soon as you substantially modify the roof structure or completely replace the roofing and thereby change the composition of the building element, this constitutes renewal and the Bbl requirement applies.
Build-up and insulation layer For a flat roof the insulation is typically between the roof deck and the roofing, or as an inverted roof on top of the waterproofing layer. For a pitched roof the insulation is between the rafters (between-rafter insulation) or on top of the roof deck (above-rafter). The thickness of the insulation package combined with the material determines the final Rc value.
The exact minimum Rc value that the Bbl requires for a roof being renewed is periodically tightened and depends on the type of structure and the situation. Always consult the current text of the Bbl or the Environment Information Point (IPLO) for the applicable requirement. What is certain: the requirement is significantly higher than what older buildings typically have. A well-insulated roof also reduces heating costs and limits overheating in summer.
On the construction drawing Tekenpunt records the roof build-up layer by layer in the cross-section drawing: structural material, vapour barrier (if applicable), insulation material with thickness, and roof covering. This allows the municipality to verify whether the build-up achieves the required Rc value. When you provide a structural calculation or EPC calculation, the drawing connects to it seamlessly.
Facade insulation: outer leaf, cavity wall and inner leaf
Renewing a facade cladding or building up the facade of an extension: both situations bring insulation requirements with them. In existing Dutch housing construction you encounter three common constructions: the cavity wall (an outer leaf, a cavity and an inner leaf), a solid wall, and a timber-frame or steel-frame facade.
Cavity wall insulation In a cavity wall, the insulation sits inside the cavity. If you are renewing the exterior facade and that makes the cavity accessible, that is the moment to fill the cavity or replace the insulation package with a material with a higher Rc value. Retroactive cavity filling (without replacing the outer facade) generally does not fall under a permit-required building activity, but that changes with an extensive facade renewal.
External facade insulation A popular approach in facade renovation is applying an insulation system to the exterior of the existing building element (ETICS, also known as facade insulation with render or cladding). This significantly increases the Rc value without altering the interior. The advantage: thermal bridging and moisture problems are largely kept outside the structure.
Facade of a new extension With an extension or addition, you build an entirely new building component. That new building component is assessed against the renovation requirement of the Bbl (not the new-construction requirement), but the difference is small in practice. You must incorporate a good insulation package into the facade structure to meet the requirement.
On the construction drawing Tekenpunt draws the facade build-up in the cross-section and lists the layers: outer leaf with material type, cavity or insulation layer with thickness, and inner leaf. For external insulation systems, the system package with thickness is stated. This way the Rc value can be reconstructed from the drawing. Facade drawings show the cladding and detailing at the facade top, window sills and corners, so the contractor can handle the thermal bridges correctly.
Floor insulation and the ground-floor slab
The ground-floor slab is a building element that is regularly renewed during renovations: a concrete floor being raised, a timber floor being replaced or a new floor for an extension. The Bbl requirement also applies here as soon as you renew the building element.
Types of floor construction The most common situations are:
- Concrete floor on the ground: insulation is usually applied under the screed (floor insulation panels), sometimes under the structural floor.
- Timber floor over a crawl space: insulation can be applied between the beams from below (blown-in or panels), or hung on the underside of the beams.
- New floor in an extension: here you start with a clean design and can optimise the insulation layer thickness from the outset.
Moisture management and vapour barrier With floor insulation, moisture plays a role. Insulation that gets wet loses its effectiveness. For concrete floors on the ground, a vapour-retarding membrane or a ventilated construction is required to prevent condensation within the structure. Tekenpunt indicates this on the section drawing so the contractor knows how the moisture barrier is incorporated in the build-up.
Comfort and energy saving A well-insulated floor immediately increases living comfort: cold feet in winter are a thing of the past and the heating system does not need to work as hard. This translates into lower annual energy costs, especially in combination with a well-insulated roof and facade.
On the construction drawing In the cross-section Tekenpunt states the floor composition from bottom to top: structural layer, insulation material with thickness, any vapour barrier and finishing layer. For a floor above a crawl space the ventilation of the crawl space is noted so that aspect can also be assessed.
Addition and extension: all requirements at once
An extension or outbuilding is a situation where in one project you build a new roof, new facades and a new floor. All three building elements then fall simultaneously under the Bbl requirement. That is an advantage: you do not need to puzzle with existing structures but can detail the build-up properly from the outset. Connection to the existing envelope Where the extension meets the existing dwelling (the gable end), there is a thermal bridge risk. The existing wall is generally less well insulated than the new facade of the extension. Heat losses and condensation problems can arise at the transition. Tekenpunt details this connection point in the drawing: how the insulation layers of the new extension connect to the existing structure and where a thermal bridge break is needed. Permit and assessment An extension above a certain size or at the front of the dwelling requires a permit. In the permit application you must demonstrate that the building elements comply with the Bbl. The cross-section drawing and the facade build-up are the key pieces for this. The municipality checks the Rc values against the material layers shown on the drawing. If these are missing or vague, a correction request follows. Construction drawing from €595 Tekenpunt prepares a complete drawing set for an extension: site plan, floor plans (existing and new), facade elevations and a cross-section with insulation build-up. The standard construction drawing starts from €595. Do you also need a structural calculation? We add it as an add-on (€500). If you are in a hurry, expedited delivery is available: +30% for delivery in 2 weeks (minimum €295) or +50% for delivery in 1 week (minimum €495), on top of the regular drawing work. More than 800 projects and 90% passing the aesthetics review in one go: we know what municipalities want to see.
Draught sealing: the forgotten factor in insulation
Insulation material reduces the thermal conductance of the building element itself, but leakage flows through joints, gaps and connection points can negate a large part of the insulation benefit. Draught sealing is therefore an essential part of energy-efficient renovation, and the Bbl also sets requirements for the air permeability of the building envelope.
Where are the gaps? The most vulnerable spots are:
- Frame connections on the facade: between the window frame and the brickwork or facade insulation
- Roof penetrations: ventilation, flues and installations that pass through the roof
- Floor-wall transition: the ground floor that connects to the outer leaf
- Joints in the roof structure: for a pitched roof the connections between roof boarding and facade
Airtight construction in practice Airtight construction requires that all layers run consistently and that joints are sealed with sealant, tape, or sleeves. This demands attention during execution on the building site. A drawing can prescribe the approach; the quality of the sealing depends on the contractor's skill.
On the construction drawing For execution drawings or detail drawings, Tekenpunt indicates at critical connection points how the airtight layer continues and where sealing products are applied. This is particularly relevant for larger renovations where an airtightness measurement (blower door test) is carried out or required.
How Tekenpunt records the insulation build-up on the drawing
A construction drawing is more than a floor plan. For assessment against the Bbl, the cross-section drawing and the detailing of building elements are crucial. Tekenpunt works as a drawing office, not as an architect or structural engineer: we record what you (or your contractor) choose as the build-up, and ensure that build-up is traceable and verifiable on the drawing. Cross-section with layer composition In the cross-section we draw each building element from outside to inside: all layers are named with material type and thickness. This allows the municipality or a municipal building inspector to calculate or verify the Rc value. We add the Rc value as an annotation when it is available from the client or the structural engineer. Materials legend and dimensions Alongside the section, the drawing contains a materials legend. Each layer is hatched or patterned in a way that indicates the material type (in accordance with NEN conventions for construction drawings). The thicknesses are dimensioned. This makes the drawing readable for both the municipality and the contractor. Alignment with the structural calculation If a structural calculation is prepared (by a KIWA-certified structural engineer), Tekenpunt's drawing aligns with the structural drawings. The structural engineer calculates the load-bearing structure; the drawing also shows the thermal envelope that runs through the structure. If you are in a hurry, expedited delivery is available: +30% for delivery in 2 weeks (minimum €295) or +50% for delivery in 1 week (minimum €495), on top of the regular drawing work. Our drawings are based on 800+ projects and pass the aesthetics review in one go 90% of the time. We know the submission requirements of municipalities and make sure the insulation build-up on the drawing matches what the municipality expects to see. This prevents a correction request and delays in your 8-week decision period.
Frequently asked questions
Q01Do I have to insulate my entire home if I am going to renovate?
No. The Bbl sets insulation requirements per building element that you renew or replace. Unchanged building elements may retain the existing insulation level (the legally acquired level). If you only replace the roof, the Bbl requirements apply to the roof; the facade and floor remain outside scope as long as you do not touch them.
Q02What is the Rc value and where do I find the applicable requirement?
The Rc value (in m2-K/W) is the thermal resistance of a building component: the higher, the better it insulates. The Bbl sets a minimum Rc value per building component (roof, facade, floor) and per situation (renovation or new construction). The exact values are periodically tightened. For the current requirement, consult the text of the Bbl or the Living Environment Information Point (IPLO) at iplo.nl.
Q03Does the insulation requirement for renovation differ from that for new construction?
Yes. For new construction the strictest requirement applies and the entire building must comply with the BENG energy performance requirements. For renovation, the Bbl requirement applies per building component that you renew; that requirement is generally slightly lower than the new-construction requirement but is still binding. An extension is regarded as a renovation, even though it is a new building component.
Q04Do I need a permit for insulating my roof or facade?
That depends on exactly what you are doing. Cavity wall insulation blown in without modifying the exterior facade is often permit-free. But a roof replacement or a complete facade renewal that substantially changes the building layer is generally a permit-required technical building activity. Check the environmental permit portal (omgevingsloket.nl) for your specific situation.
Q05What must be on the construction drawing to prove that I meet the insulation requirement?
The cross-section drawing must show the layer build-up of each building element to be renewed: material type and thickness of each layer, from outside to inside. The Rc value can be calculated from this. Some municipalities ask for an explicit Rc calculation as an attachment; others accept the build-up on the drawing. Tekenpunt lists the layer build-up as standard in the cross-section.
Q06Does draught sealing also count for the Bbl?
Yes. In addition to insulation requirements, the Bbl also sets requirements for the airtightness of the building envelope. Insulation material reduces heat conductivity, but gaps and unsealed connection points can negate a large part of the benefit. For larger renovations or extensions, airtightness is increasingly checked via a blower door test.
Q07Can Tekenpunt also calculate the Rc values?
Tekenpunt is a drawing office, not a structural engineering firm. We accurately record in the drawing the layer composition chosen by you or your contractor. An explicit Rc calculation or energy performance calculation (EPC) is a separate specialism performed by an adviser or structural engineer. We seamlessly align the drawing with that calculation.
Q08Does an insulation requirement also apply if I build an extension without a permit?
Permit-free building does not exempt you from the technical requirements of the Bbl. Even if an extension is permit-free, the building element must comply with the insulation requirement. The difference is that the municipality does not assess the drawings in advance. The responsibility for compliance then rests with you as the building owner.
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