Why no staples, if the membrane says you can?

With batts or boards stapling is fine. With blown-in insulation the membrane is under pressure and staples tear out. So we fix it with double-sided tape and battens.

What density do you use?

Cellulose 45-55 kg/m³, wood fibre and cardboard 35-45 kg/m³, straw 90-110 kg/m³.

Can I work in phases?

Yes, up to 3 months between membrane and blowing. Protect the membrane from light and damage and check the joints before blowing.

Can I do the blowing myself?

No, we do the blowing. That way the density is right and the insulation does not settle.

Suitable for listed buildings?

Often yes, as interior insulation does not change the facade. Consult the municipality and have it investigated beforehand.

Preparation guide

How to prepare your roof or stud wall for blown-in insulation

You do the preparation, we blow in the insulation. This guide tells you step by step what to do. In doubt? Call us, it saves you work later.

Allow 5 to 10 half-days for an average roof or wall.

Preparation for blown-in insulation: what you arrange and what we do — A bit of Reinder Douwes and a bit of AI

You take care of

Inspection for moisture and leaks
Levelling purlins or studs
Fitting the vapour membrane
Sealing the membrane with tape and sealant
Fitting battens
Preparing the wiring
Clearing the space for blowing

We take care of

Blowing in insulation under pressure
Checking density and fill
Sealing the blowing holes airtight again

Important: no staples when blowing in

We advise against stapling the vapour membrane, even though the membrane itself says you can. Blowing puts pressure on the membrane and staples tear out. Every torn staple is a hole in your airtight layer. Fix the membrane temporarily with double-sided tape on the timber and screw the battens on straight away. The battens hold membrane and insulation in place.

At what density do we blow in?

Material	Density
Cellulose	45 - 55 kg/m³
Wood fibre	35 - 45 kg/m³
Cardboard	35 - 45 kg/m³
Straw	90 - 110 kg/m³

Straw is heavier. For straw, use rafters and battens one size heavier than the table in step 2.

1. How does the system work?

Three layers work together. The inner two are your work.

Layer	Who	What does it do?
Vapour membrane (Intello Plus)	You, beforehand	Smart vapour control: keeps moisture out in winter, lets it dry in summer (sd 0.25 to 10 m).
Blown-in insulation	Us	Fills every gap, no thermal bridges, good sound damping.
Battens + plasterboard	You	Hold membrane and insulation, leave room for wiring and form the base for the finish.

A single 1 mm gap lets up to 800 grams of moisture per metre of joint into the construction each day. That is 1600 times more than through a properly fitted membrane. Airtightness is not a detail.

Airtight layer on the warm side, vapour-open on the outside

A leak in the membrane: warm, moist air flows into the insulation

A 1 mm gap lets through a lot of moisture, so every seam matters

Smart membrane: protection in winter, drying out in summer

2. Materials, tools and sizing

Material	Amount	Purpose
Intello Plus membrane (1.50 or 3.00 m)	m² + 20%	The vapour membrane
Double-sided tape (e.g. Duplex)	Along every rafter	Temporary fixing, instead of staples
Tescon Vana tape 60 mm	1 roll per 30 m²	Overlaps and joints on timber
Orcon F sealant	2 tubes per 30 m²	Joints on brick, concrete and plaster
Tescon Profect / Contega SL	Per window	Window corners and gaps at frames
Roflex / Kaflex grommets	Per penetration	Cables and pipes through the membrane
Rafters or studs C24	See table	Supporting structure
Battens according to purlin span table (C18)	300 mm centres	Hold membrane and insulation, base for plasterboard
Screws 35-40 mm	Per crossing	Fixing battens

Insulation thickness	Rc	Suitable for
130 mm	3.5	Recommended minimum
150 mm	4.0	Comfortable and future-proof
185 mm	5.0	Near energy-neutral
222 mm	6.0	Passive house level

Purlin span	Insulation thickness	Rafter	Centres
1.05 m	up to 200 mm	21 x 58 mm	300 mm
1.05 m	from 200 mm	28 x 58 mm	300 mm
1.50 m	up to 200 mm	28 x 70 mm (or 28 x 58)	300 mm (or 200)

Wall insulation thickness	Stud	Note
80 - 100 mm	44 x 69 mm	Anchoring to wall required
100 - 140 mm	38 x 100-120 mm (SLS)	Most common
140 - 220 mm	38 x 140-195 mm	Heavy construction

Tools: screwdriver, sealant gun, cutter, tape measure, level with a metal straightedge over 2 m and a pressure roller. Span of 1.50 m? Call us first, structural advice is needed.

3. Inspection before anything else

Purlins and rafters are sound and load-bearing.
No moisture, mould or active leaks.
Check for a vapour-open windproof layer outside. If there is none, the inner membrane is even more important.
Gaps larger than 5 mm are sealed beforehand.
Timber moisture below 20% (use a moisture meter).
Walls: at least one brick thick (approx. 21 cm), no rising damp. Remove cement render and synthetic finishes.
Flue: enclosure of non-combustible material filled with stone wool, keep the manufacturer's clearance. Cellulose withstands up to 70 °C.

Moisture problem? Stop. Fix the cause first and let it dry to below 20% timber moisture.

4. Levelling

All purlins or studs must lie in one plane. An uneven plane causes bulges, gaps and a crooked finish later.

1Pick the most protruding purlin as reference.
2Lay the metal straightedge across the purlins and find the low spots.
3Pack low purlins with a batten until the straightedge touches everywhere.
4Maximum deviation 3 mm. Packing more than 50 mm? Call us first.
5Walls: plates on floor and ceiling, hammer plugs at 500 mm, studs at 600 mm, 10 mm clear of the wall.

5. Fitting the membrane, without staples

The printed side faces you. Roll out bottom to top (roof) or left to right (wall).

1Measure the length and add 40 mm at both edges for the connection.
2Apply double-sided tape to the rafters or studs.
3Press the membrane taut onto the tape, no creases or sagging. Do not staple.
4Next strip with 100 mm overlap, use the printed lines.
5Screw the battens onto the membrane as soon as possible (step 7). They hold it during blowing.
6Wrap window reveals fully and tape them to the frame.

The membrane says stapling is allowed. For blown-in insulation we advise against it: blowing pressure tears staples out and creates holes in the airtight layer. Already stapled? Cover every staple with Tescon Vana.

Membrane with the battens screwed on straight away

6. Sealing joints, edges and corners

The most important step: around 80% of air leaks are here. Take your time.

Overlaps: Tescon Vana centred on the overlap, crease-free, rubbed down firmly with the roller.
Brick, concrete or plaster: dust-free surface, a 10-15 mm bead of Orcon F, press the membrane in within 10 minutes with a small loop.
Timber: tape half on timber and half on membrane, or Orcon F on uneven timber.
Corners: Tescon Profect, stick one leg first, then the second.
Floor to wall junction: lay a waiting strip of membrane, so no draught enters the insulation via the floor joint.
Tape sticks poorly below 5 °C or on dust and moisture.

Press the tape firmly with the applicator

Sealant bead on the timber for the junction

Pressing the membrane into the sealant at the junction

7. Fitting battens (before blowing)

Battens according to the purlin span table in step 2 (21 x 58 mm, 28 x 58 mm or 28 x 70 mm), at least C18, perpendicular to purlins or studs.
300 mm centres (max. 500 mm).
Screw at every crossing, screws at least 35 mm.
This creates approx. 20 mm service space for wiring.

Battens along the edges do not replace sealant and tape. Seal first, then fit battens.

8. Preparing the wiring

Make a wiring plan first to avoid holes.
Cables in the 20 mm space between battens, clips on the batten and never on the membrane.
Water and heating pipes do not belong in the service space.
Back boxes on the batten or on blocks, flush with the finish.
Every penetration with a Roflex grommet, never just cut a hole. Bundle cables.
No recessed spotlights: choose surface spots or LED panels.

9. Ready for our visit

Rooms empty and easy to reach.
2 x 230 V on different circuits (16 A).
We make the blowing holes (approx. 1 per 3-4 m²) and tape them crosswise and square afterwards.
On walls the holes are in the top third and we check extra near the floor.
The membrane may bulge slightly, but not stretch excessively.

Start with the plasterboard within 48 hours of blowing. Do not use OSB, plywood or underlayment: they block the membrane. Plasterboard or vapour-open wood fibre board is fine.

10. Quality and common mistakes

Mistake	Solution
Membrane stapled	No staples when blowing. Double-sided tape and battens straight away.
Membrane not taut	Pull tighter, battens at 300 mm.
Overlap poorly taped	Rub down fully with the roller.
Edges poorly sealed	Enough sealant, take your time.
Penetration not sealed	Always grommet, tape or sealant.
OSB or plywood as finish	Vapour-open boards only.
Poor levelling	Metal straightedge, max. 3 mm deviation.
Small tear in membrane	Up to 10 mm: Tescon Vana 50 mm over it. Larger: sealant plus tape.

Test yourself with a smoke pencil under low pressure: if smoke is drawn in, there is a leak. A blower door test gives a hard measurement.

Frequently asked questions

Unsure about something?

Call or message us. Better to check now than have a problem later.

Call +31 10 30 70 148 Price indication