8W Open-Cell Spray Foam | Rayston Thermal & Acoustic Insulation
Contents
- What is 8W open-cell spray foam and when should you specify it?
- CO₂ blowing agent and two-component system make-up
- Foam properties: density, open cells, λ, μ, fire and emissions
- Declared acoustic performance
- Aged thermal performance table (thickness / λ / R)
- Component properties and laboratory reactivity
- Storage, packaging, equipment cleaning and empty containers
- 8W vs other Rayston grades: which one to choose?
- 8W open-cell spray foam: FAQ
- Engineering summary
- Related links
Rayston Spray Foam 8W by Krypton Chemical: a 95% open-cell spray polyurethane foam with 8–10 kg/m³ density, λ = 0.038 W/m·K and declared sound insulation of 40–44 dB, blown with CO₂ — all figures from the technical datasheet.
- Product: Rayston Spray Foam 8W
- Grade: 8W · open-cell
- Application: spray-applied thermal and acoustic insulation
8W spray foam (Rayston Spray Foam 8W) is a two-component spray polyurethane foam system from Krypton Chemical, S.L., formulated to produce a semi-rigid, open-cell foam. Its only blowing agent is carbon dioxide (CO₂) generated by the reaction between the two components (ODP = 0). Sprayed density reaches 8–10 kg/m³, declared thermal conductivity is λ = 0.038 W/(m·K) and open-cell content is 95%, with declared sound insulation values of 40 dB and 44 dB depending on the plasterboard build-up, according to the official technical datasheet (last revised 02/06/2026).
This article covers one grade of the Rayston Spray Foam range. To compare all grades, see the general guide: spray polyurethane foam. For the published closed-cell HFO grade, see HFO 40 spray foam.
01
What is 8W open-cell spray foam and when should you specify it?
8W spray foam (Rayston Spray Foam 8W) is a two-component (A+B) polyurethane system that produces a semi-rigid, open-cell foam. It is applied with dedicated spray equipment to form a continuous interior thermal and acoustic insulation layer.
Use declared in the datasheet: interior thermal and acoustic insulation of:
- Roofs and attics
- Timber, masonry and steel walls
- Lightweight construction systems in residential, public and industrial buildings
- Hangars built on site (in situ)
Sprayed density reaches 8–10 kg/m³, depending on pass thickness and workmanship. This low density, combined with 95% open-cell content, sets the grade apart from the closed-cell lines (W and HFO) in the Rayston range.
Manufacturer: kryptonchemical.com.
Internal links: Knowledge base · Products · Documents.
02
CO₂ blowing agent and two-component system make-up
8W spray foam relies on a single declared blowing agent: carbon dioxide (CO₂) generated by the reaction between the two components, with ODP = 0. In terms of cell structure and use, this places it outside the HFO family (HFO 35 / HFO 40 / HFO 50) and outside the explicitly water-blown grades of the rigid W line.
The two components according to the datasheet:
Component A: polyol blend, a yellowish liquid with no suspended particles.
Component B: a blend of aromatic polyisocyanates, mainly diphenylmethane diisocyanate (MDI); a dark brown liquid with no suspended particles.
The 8W datasheet does not give a designation code of the PU EN 14315-1-… type used for the rigid grades. Nor does the 8W sheet list mix ratios or spray windows as the rigid line does; application is declared via dedicated spraying equipment, with the laboratory properties below.
03
Foam properties: density, open cells, λ, μ, fire and emissions
Applied (sprayed) density
8–10 kg/m³
Depends on thickness and workmanship
Free-rise density (lab, 25 °C)
8 kg/m³
Laboratory conditions
Open cells
95%
ASTM D2856
Water vapour permeability factor μ
μ = 4.6
EN12086
Vapour resistance at 200 mm
0.93 SD
EN12086
Water permeability
< 13.8 kg/m²
EN1609
VOC emissions
Class A
EN ISO 16000
Other emissions
< 1 μg/m³
EN ISO 16000
Non-emission (declared)
Ok
NF EN ISO 16000-3/6/9/11
Gross heat of combustion (PCS 4)
0.22
EN ISO1716
| Property | Value | Standard / TDS reference |
|---|---|---|
| Applied (sprayed) density | 8–10 kg/m³ | Depends on thickness and workmanship |
| Free-rise density (lab, 25 °C) | 8 kg/m³ | Laboratory conditions |
| Closed cells | CCC1 | ISO4590 |
| Open cells | 95% | ASTM D2856 |
| Declared thermal conductivity λ | 0.038 W/(m·K) | EN 12667:2001 |
| Water vapour permeability factor μ | μ = 4.6 | EN12086 |
| Vapour resistance at 200 mm | 0.93 SD | EN12086 |
| Water permeability | < 13.8 kg/m² | EN1609 |
| Reaction to fire | Euroclass F | EN13501-1:2007 |
| Reaction to fire after ageing | Ok | EN14315-1:2013 |
| VOC emissions | Class A | EN ISO 16000 |
| Other emissions | < 1 μg/m³ | EN ISO 16000 |
| Non-emission (declared) | Ok | NF EN ISO 16000-3/6/9/11 |
| Gross heat of combustion (PCS 4) | 0.22 | EN ISO1716 |
Brief engineering notes:
- λ = 0.038 is higher than the closed-cell grades in the range (e.g. HFO 40 at 0.028), which is consistent with a lightweight open-cell structure.
- μ = 4.6 is far lower than the μ ≥ 60–80 of the rigid W/HFO grades; on the declared figure, this grade is much more vapour-open.
- Reaction to fire is declared as Euroclass F to EN13501-1:2007, unlike the Class E declared for the closed-cell grades of the same range.
- No numerical compressive strength is given for 8W in the datasheet.
04
Declared acoustic performance
8W spray foam is the grade that declares numerical acoustic values among the available Rayston Spray Foam datasheets:
| Build-up | Sound insulation | Standard |
|---|---|---|
| 195 mm foam + plasterboard 1×13 mm | 40 dB | EN10140-2 |
| 195 mm foam + plasterboard 2×13 mm | 44 dB | EN10140-2 |
These values relate to the build-up declared in the datasheet; do not extrapolate them to other thicknesses without further data from the manufacturer.
05
Aged thermal performance table (thickness / λ / R)
For 8W spray foam, λ = 0.038 stays the same for every thickness listed in the aged performance table, and thermal resistance R rises in direct proportion to thickness. The datasheet table starts at 50 mm (not 30 mm), and above 140 mm the steps become 10 mm.
R (m²·K/W)
Aged λ (W/m·K) 0.038 · thickness 50–200 mm
50 mm
1.28
55 mm
1.45
60 mm
1.58
65 mm
1.71
70 mm
1.84
75 mm
1.97
80 mm
2.10
85 mm
2.24
90 mm
2.37
95 mm
2.50
100 mm
2.63
105 mm
2.76
110 mm
2.89
115 mm
3.03
120 mm
3.16
125 mm
3.29
130 mm
3.42
135 mm
3.55
140 mm
3.68
150 mm
3.95
160 mm
4.21
170 mm
4.47
180 mm
4.74
190 mm
5.00
200 mm
5.26
Worked example: at 50 mm the grade achieves R = 1.28 m²·K/W. At 100 mm this becomes R = 2.63, and at 200 mm it reaches R = 5.26 — with λ = 0.038 in every declared row.
| Thickness (mm) | Aged λ (W/m·K) | R (m²·K/W) |
|---|---|---|
| 50 | 0.038 | 1.28 |
| 55 | 0.038 | 1.45 |
| 60 | 0.038 | 1.58 |
| 65 | 0.038 | 1.71 |
| 70 | 0.038 | 1.84 |
| 75 | 0.038 | 1.97 |
| 80 | 0.038 | 2.10 |
| 85 | 0.038 | 2.24 |
| 90 | 0.038 | 2.37 |
| 95 | 0.038 | 2.50 |
| 100 | 0.038 | 2.63 |
| 105 | 0.038 | 2.76 |
| 110 | 0.038 | 2.89 |
| 115 | 0.038 | 3.03 |
| 120 | 0.038 | 3.16 |
| 125 | 0.038 | 3.29 |
| 130 | 0.038 | 3.42 |
| 135 | 0.038 | 3.55 |
| 140 | 0.038 | 3.68 |
| 150 | 0.038 | 3.95 |
| 160 | 0.038 | 4.21 |
| 170 | 0.038 | 4.47 |
| 180 | 0.038 | 4.74 |
| 190 | 0.038 | 5.00 |
| 200 | 0.038 | 5.26 |
06
Component properties and laboratory reactivity
Component A (polyol)
Description: Polyol blend, yellowish liquid, no suspended particles
Density at 20 °C: 1.10 ± 0.02 g/cm³
Viscosity at 20 °C: 600 ± 100 mPa·s
Component B (isocyanate)
Description: Aromatic polyisocyanates (mainly MDI), dark brown, no suspended particles
Density at 20 °C: 1.22 ± 0.02 g/cm³
Viscosity at 20 °C: 350 ± 100 mPa·s
Free-rise foam properties under laboratory conditions:
Cream time
3–4 s
Rise (expansion) time
5–7 s
Foam density at 25 °C
8 kg/m³
| Property | Component A (polyol) | Component B (isocyanate) |
|---|---|---|
| Description | Polyol blend, yellowish liquid, no suspended particles | Aromatic polyisocyanates (mainly MDI), dark brown, no suspended particles |
| Density at 20 °C | 1.10 ± 0.02 g/cm³ | 1.22 ± 0.02 g/cm³ |
| Viscosity at 20 °C | 600 ± 100 mPa·s | 350 ± 100 mPa·s |
| Property | Value |
|---|---|
| Cream time | 3–4 s |
| Rise (expansion) time | 5–7 s |
| Foam density at 25 °C | 8 kg/m³ |
These are reference laboratory times. The 8W datasheet does not give volume/weight mix ratios or ranges for component temperature, working pressure or humidity/wind as the rigid grades do; application is declared via dedicated spraying equipment only.
07
Storage, packaging, equipment cleaning and empty containers
Packaging
Steel drums of approx. 200 dm³ and IBC containers of approx. 1000 dm³.
Storage and shelf life
Store in a dry place at above 0 °C, protected from moisture. Storage life: 6 months in the original, tightly sealed drums. Once a drum has been partly used, reseal the remainder tightly and use it promptly.
Equipment cleaning
After application, clean the machine carefully to avoid contaminating the next system when a different system is run on the same rig. (The 8W datasheet does not name a specific commercial cleaning fluid.)
Empty containers and environment
Handle empty containers with the same precautions as full ones and hand them over as hazardous waste to a licensed waste manager. A and B can be mixed 1/1 to obtain an inert material, provided the quantity does not exceed 5 litres, to avoid a dangerous build-up of heat. Do not mix residues with any other product without knowing the possible reactions.
The manufacturer’s recommendations do not relieve the applicator of reviewing the application method and running preliminary trials whenever there is doubt about the system’s suitability for site conditions.
08
8W spray foam vs other Rayston grades: which one to choose?
Choosing a grade is a design decision driven by the application, cell structure, density, λ, μ and acoustic requirements — not by the trade name alone. Within what the 8W datasheet figures support:
1
Declared interior thermal + acoustic insulation, 95% open cells, 8–10 kg/m³ density, CO₂-blown → 8W is the direct candidate.
2
Closed cells > 90%, declared λ 0.028 and μ ≥ 80 within the HFO range → see HFO 40 spray foam, or HFO 35 spray foam and HFO 50 spray foam.
3
Water-blown, with higher densities and λ ≈ 0.030–0.031 → compare 30W / 40W / 50W in the general guide when you need a rigid foam.
4
A numerical compressive strength declared in the datasheet → not available for 8W; see 50W spray foam and HFO 50 spray foam.
This section does not replace a thermal or acoustic calculation for the building, nor the technical datasheet of the selected grade. For the full comparison table, see the spray polyurethane foam guide.
09
8W open-cell spray foam: FAQ
What is 8W spray foam, in short?
A two-component polyurethane system (Rayston Spray Foam 8W) from Krypton Chemical that produces a semi-rigid, open-cell foam, blown by CO₂ from the component reaction, with an applied density of 8–10 kg/m³, for interior thermal and acoustic insulation.
Is 8W spray foam open-cell or closed-cell?
Open-cell: 95% open cells (ASTM D2856), closed-cell classification CCC1 (ISO4590).
What is the declared thermal conductivity?
λ = 0.038 W/(m·K) to EN 12667:2001. In the ageing table, λ stays at 0.038 for every listed thickness from 50 to 200 mm.
What are the declared sound insulation values?
40 dB with 195 mm of foam + 1×13 mm plasterboard, and 44 dB with 195 mm + 2×13 mm boards, to EN10140-2.
What is the blowing agent?
Only CO₂ generated by the component reaction, with ODP = 0.
What is the reaction-to-fire classification?
Euroclass F to EN13501-1:2007, with reaction to fire after ageing declared as “Ok” to EN14315-1:2013.
Where can I compare 8W with HFO 40 and the W grades?
In the spray polyurethane foam guide, and in the HFO 40 spray foam article for the published closed-cell grades.
10
Engineering summary
8W spray foam (Rayston Spray Foam 8W) is the semi-rigid, open-cell grade in Krypton Chemical’s Rayston line: CO₂-blown (ODP = 0), applied density 8–10 kg/m³, 95% open cells, declared λ of 0.038 with a constant λ in the ageing table from 50 to 200 mm, μ = 4.6, declared sound insulation of 40 / 44 dB with a 195 mm + plasterboard build-up, VOC emissions Class A and reaction to fire Euroclass F. Its declared use is interior thermal and acoustic insulation of roofs, attics, walls, lightweight structures and hangars. Confirm the final choice against the datasheet figures and the project thickness, and refer to the general guide and HFO 40 when comparing with the closed-cell grades.
11
Related links
General guide and published grades
Grade articles
8W
Rayston Spray Foam 8W
| Grade | Trade name | Article |
|---|---|---|
| 8W | Rayston Spray Foam 8W | This article |
| 30W | Rayston Spray Foam 30W | 30W spray foam |
| 40W | Rayston Spray Foam 40W | 40W spray foam |
| 50W | Rayston Spray Foam 50W | 50W spray foam |
| HFO 35 | Rayston Spray Foam HFO 35 | HFO 35 spray foam |
| HFO 40 | Rayston Spray Foam HFO 40 | HFO 40 spray foam |
| HFO 50 | Rayston Spray Foam HFO 50 | HFO 50 spray foam |
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