Spray Polyurethane Foam (SPF) Insulation: Rayston Grade Guide
Contents
- What is spray polyurethane foam and why use it for thermal insulation?
- How does a two-component spray system work?
- Open-cell vs closed-cell spray foam: cell structure compared
- Blowing agents: water-blown (W range) vs HFO technology (HFO range)
- Rayston Spray Foam grade comparison table
- How to read lambda (λ) and R-values from the datasheet
- Which grade for interior walls and ceilings?
- When to choose a higher-density or compression-rated grade
- What site application conditions do the grades share?
- Safety, storage and equipment cleaning
- Spray polyurethane foam FAQ
- Grades — individual articles
- Engineering summary
An engineering guide to the Rayston Spray Foam range from Krypton Chemical: 8W, 30W, 40W, 50W and HFO grades compared by density, lambda (λ) and closed-cell content, using data from the technical datasheets.
- Product: Rayston Spray Foam
- Grades: 8W · 30W · 40W · 50W · HFO
- Application: spray-applied thermal insulation
01
What is spray polyurethane foam and why use it for thermal insulation?
Spray polyurethane foam (SPF) is a thermal insulation system sprayed directly onto the substrate with dedicated mixing equipment. Two liquid components — polyol and isocyanate — react and expand in place to form a continuous, fully adhered insulation layer that seals corners and construction joints without mechanical fixings.
Krypton Chemical (Krypton Chemical, S.L.) has developed the Rayston Spray Foam range to cover lightweight open-cell grades, rigid water-blown grades (W range) and rigid grades with advanced blowing agents (HFO/HCFO range). This guide gives contractors, designers and consultants a practical engineering reference for comparing the grades and selecting the right system against the requirements stated in the technical datasheets (TDS).
Manufacturer website: kryptonchemical.com.
02
How does a two-component spray system work?
In Rayston spray polyurethane foam systems, the two components are mixed at a set volume ratio (typically 100:100 by volume for the rigid grades covered here), with weight ratios that vary slightly by grade, and sprayed at a working pressure within the datasheet range. The result is insulation formed in place: it bonds to the substrate and limits the thermal bridging that hand-cut boards leave behind.
What changes from one grade to the next?
Blowing agent:
Water (W range), HFO/HCFO (HFO range), or the CO₂ generated by the reaction in 8W.
Cell structure:
Semi-rigid open-cell (8W) versus rigid foam with a higher closed-cell content (especially the HFO grades).
Applied density, thermal conductivity λ and water vapour diffusion resistance μ.
Additional declared use:
Acoustic insulation for 8W, and higher compressive requirements for 50W and HFO 50, as stated in the official technical datasheets.
03
Open-cell vs closed-cell spray foam: cell structure compared
Open-cell — Rayston Spray Foam 8W
Rayston Spray Foam 8W is a two-component system that produces a semi-rigid, open-cell polyurethane foam. Its only blowing agent is the CO₂ generated by the reaction between the two components (ODP = 0 according to the official technical datasheets). Applied density reaches 8–10 kg/m³ depending on thickness and workmanship; free-rise laboratory density is about 8 kg/m³ at 25 °C.
Properties recorded in the official technical datasheets:
- Open cells approx. 95% (ASTM D2856) and closed-cell class CCC1 (ISO 4590).
- Aged thermal conductivity 0.038 W/(m·K).
- Water vapour permeability μ = 4.6 (EN 12086).
- Sound insulation: 40 dB at 195 mm + 13 mm plasterboard, and 44 dB with two 13 mm boards (EN 10140-2).
- VOC emissions: Class A (EN ISO 16000).
- Reaction to fire: Euroclass F (EN 13501-1:2007).
- Declared use: interior thermal and acoustic insulation of roofs, lofts, timber walls, masonry and lightweight structures in residential, public and industrial buildings and hangars, applied on site.
Closed-cell / rigid grades — W and HFO ranges
Grades 30W / 40W / 50W and HFO 35 / HFO 40 / HFO 50 are rigid spray-applied polyurethane foam systems. The HFO range declares a closed-cell content of > 90%. For the W range, the datasheet tables list closed-cell content as < 80% (30W and 40W) and < 70% (50W).
Declared use common to the rigid grades: spray-applied thermal insulation on surfaces not subject to permanent loads, such as vertical walls and ceilings from the inside. On façades it repels water while still allowing the construction to breathe to some degree.
04
Blowing agents: water-blown (W range) vs HFO technology (HFO range)
W range — water-blown
The 30W, 40W and 50W grades use water as the main blowing agent. The technical description confirms that the formulation is free of ozone-depleting substances and fluorinated greenhouse gases (no HFC, HCFC or VOC according to the official technical datasheets). The range keeps a stable thermal conductivity (λ) from installation throughout the life of the product, and the foam is 100% mechanically recyclable, with no need to capture gases for recycling or disposal.
HFO range — blowing agent technology (HFO / HCFO)
- HFO 35 and HFO 40: blown with HFO (trans-1-chloro-3,3,3-trifluoropropene).
- HFO 50: the gas held in its cells is 1-chloro-3,3,3-trifluoro-propene (HCFO-1233zd(E)), and the formulation contains no HCFC or HFC.
From a design point of view, the HFO range achieves a lower declared thermal conductivity (λ = 0.028 W/m·K for HFO 35/40; the HFO 50 property table declares 0.021 W/m·K, with an ageing table starting at 0.028), a closed-cell content above 90% and a higher water vapour diffusion resistance factor (μ ≥ 80).
05
Rayston spray polyurethane foam grades compared (datasheet values only)
8W
Rayston Spray Foam 8W
Structure / blowing: Open / reaction CO₂
Applied density (kg/m³): 8–10
Declared λ (W/m·K): 0.038
Closed cells: CCC1 / open ≈95%
μ: 4.6
Reaction to fire: Euroclass F
TDS notes: Sound insulation 40–44 dB; VOC Class A
30W
Rayston Spray Foam 30W
Structure / blowing: Rigid / water
Applied density (kg/m³): 28–35
Declared λ (W/m·K): 0.031
Closed cells: < 80%
μ: ≥ 60
Reaction to fire: Class E
TDS notes: Mix ratio 100:100 vol / 100:108 wt
40W
Rayston Spray Foam 40W
Structure / blowing: Rigid / water
Applied density (kg/m³): 38–42
Declared λ (W/m·K): 0.031
Closed cells: < 80%
μ: ≥ 70
Reaction to fire: Class E
TDS notes: Mix ratio 100:100 vol / 100:108 wt
50W
Rayston Spray Foam 50W
Structure / blowing: Rigid / water
Applied density (kg/m³): 48–56
Declared λ (W/m·K): 0.030
Closed cells: < 70%
μ: ≥ 70
Reaction to fire: Class E
TDS notes: Compressive strength 280 / ≥200 kPa; CS (10/Y)200
HFO 35
Rayston Spray Foam HFO 35
Structure / blowing: Rigid / HFO
Applied density (kg/m³): 30–40
Declared λ (W/m·K): 0.028
Closed cells: > 90%
μ: ≥ 80
Reaction to fire: Class E
TDS notes: Ratio 100:100 vol / 100:110 wt
HFO 40
Rayston Spray Foam HFO 40
Structure / blowing: Rigid / HFO
Applied density (kg/m³): 42–47
Declared λ (W/m·K): 0.028
Closed cells: > 90%
μ: ≥ 80
Reaction to fire: Class E
TDS notes: Ratio 100:100 vol / 100:110 wt
HFO 50
Rayston Spray Foam HFO 50
Structure / blowing: Rigid / HCFO-1233zd(E)
Applied density (kg/m³): 48–55
Declared λ (W/m·K): 0.021 (properties); ageing table 0.028→0.025
Closed cells: > 90%
μ: MU80 in designation code
Reaction to fire: Class E
TDS notes: For use where a compressive strength > 200 kPa is required
Short-term water absorption for the rigid grades that declare it: ≤ 0.2 kg/m².
The values above summarise the common comparison fields only; see each grade’s technical datasheet for full details.
| Grade | Trade name | Structure / blowing | Applied density (kg/m³) | Declared λ (W/m·K) | Closed cells | μ | Reaction to fire | TDS notes |
|---|---|---|---|---|---|---|---|---|
| 8W | Rayston Spray Foam 8W | Open / reaction CO₂ | 8–10 | 0.038 | CCC1 / open ≈95% | 4.6 | Euroclass F | Sound insulation 40–44 dB; VOC Class A |
| 30W | Rayston Spray Foam 30W | Rigid / water | 28–35 | 0.031 | < 80% | ≥ 60 | Class E | Mix ratio 100:100 vol / 100:108 wt |
| 40W | Rayston Spray Foam 40W | Rigid / water | 38–42 | 0.031 | < 80% | ≥ 70 | Class E | Mix ratio 100:100 vol / 100:108 wt |
| 50W | Rayston Spray Foam 50W | Rigid / water | 48–56 | 0.030 | < 70% | ≥ 70 | Class E | Compressive strength 280 / ≥200 kPa; CS (10/Y)200 |
| HFO 35 | Rayston Spray Foam HFO 35 | Rigid / HFO | 30–40 | 0.028 | > 90% | ≥ 80 | Class E | Ratio 100:100 vol / 100:110 wt |
| HFO 40 | Rayston Spray Foam HFO 40 | Rigid / HFO | 42–47 | 0.028 | > 90% | ≥ 80 | Class E | Ratio 100:100 vol / 100:110 wt |
| HFO 50 | Rayston Spray Foam HFO 50 | Rigid / HCFO-1233zd(E) | 48–55 | 0.021 (properties); ageing table 0.028→0.025 | > 90% | MU80 in designation code | Class E | For use where a compressive strength > 200 kPa is required |
06
How to read lambda (λ) and R-values from the datasheet
The technical datasheets (TDS) for the rigid grades include detailed performance tables that link applied thickness (mm) to:
- the aged thermal conductivity λ in W/(m·K);
- the resulting thermal resistance R in m²·K/W.
0.038
λ · 8W
0.031
λ · 30W / 40W
0.030
λ · 50W
0.028
λ · HFO 35 / HFO 40
Indicative comparison at 50 mm thickness (from the TDS performance tables):
- 8W: λ = 0.038 gives R ≈ 1.28.
- 30W / 40W: λ = 0.031 gives R ≈ 1.60.
- 50W: λ = 0.030 gives R ≈ 1.70.
- HFO 35 / HFO 40: λ = 0.028 gives R ≈ 1.80.
- HFO 50: the ageing table gives λ = 0.028 and R ≈ 1.80 at 50 mm (while the initial, non-aged properties declare λ = 0.021 W/m·K).
R increases in proportion to thickness, and for some HFO grades the aged λ falls at greater thicknesses (HFO 40, for example, reaches 0.026 W/m·K in the higher thickness bands). Base the project’s thermal calculations on the target-thickness row of each product’s own performance table.
07
Which spray polyurethane foam grade for interior walls and ceilings?
The common wording in the rigid-grade datasheets states that the product is intended for spray-applied thermal insulation on surfaces not subject to permanent loads, such as vertical walls and interior ceilings. 8W explicitly extends this to interior thermal and acoustic insulation of roofs, lofts, walls of all types, lightweight structures and hangars.
How to choose a grade for an interior surface
1
Declared acoustic requirement + very low density: start with 8W and the sound insulation figures in its datasheet.
2
Rigid, water-blown thermal insulation at medium density: 30W (28–35 kg/m³) or 40W (38–42 kg/m³).
3
Higher density within the W range, with declared compressive strength: 50W.
4
Closed cells > 90% and declared λ 0.028: HFO 35 or HFO 40, depending on the density range required.
5
Density 48–55 kg/m³ with a stated compressive strength > 200 kPa: HFO 50.
This table does not replace a thermal calculation for the building; select thickness and R-value from the performance tables in each datasheet to meet the design requirement.
08
When to choose a higher-density or compression-rated spray foam
50W: applied density 48–56 kg/m³, stated compressive strength 280 with a limit of ≥ 200 kPa, and a designation code that includes CS (10/Y)200.
HFO 50: applied density 48–55 kg/m³; according to the technical datasheets it is suitable for applications that require a compressive strength greater than 200 kPa.
The lighter grades (8W, then 30W) show no comparable compressive values in their datasheets.
Permanent loads: the rigid-grade datasheets state that these grades are not intended for applications under permanent load. Any use outside this scope requires an engineering decision and a review of the relevant documents — beyond the scope of this general article.
09
Common site conditions for applying spray polyurethane foam
The following conditions recur in the rigid-grade datasheets (W and HFO), with minor differences:
Component temperature
30–60 °CHFO 50: 25–45 °C
Working pressure
60–120 barAll grades
Ambient temperature
0 to 40 °CAll grades
Relative air humidity
< 90%All grades
Wind speed
< 30 km/hAll grades
Substrate temperature
5–40 °C50W: 0–40 °C
Substrate moisture
No surface condensationAll grades
Mix ratio by volume
100:100Common to this range
Mix ratio by weight
100:108 (30W/40W) · 100:107 (50W) · 100:110 (HFO)Varies by grade
| Condition | Typical TDS value (rigid grades) | Variations |
|---|---|---|
| Component temperature | 30–60 °C | HFO 50: 25–45 °C |
| Working pressure | 60–120 bar | All grades |
| Ambient temperature | 0 to 40 °C | All grades |
| Relative air humidity | < 90% | All grades |
| Wind speed | < 30 km/h | All grades |
| Substrate temperature | 5–40 °C | 50W: 0–40 °C |
| Substrate moisture | No surface condensation | All grades |
| Mix ratio by volume | 100:100 | Common to this range |
| Mix ratio by weight | 100:108 (30W/40W) · 100:107 (50W) · 100:110 (HFO) | Varies by grade |
8W is processed with dedicated spray equipment; declared laboratory times: cream time 3–4 s, rise time 5–7 s.
10
Safety, storage and equipment cleaning
Occupational safety
Component B of the rigid grades contains isocyanates. Follow the safety data sheet (MSDS): good ventilation and/or respiratory protection (organic vapour + particulate filters) with protective clothing. These products are for industrial and professional use only and are not suitable for DIY.
Storage
- Rigid grades: store components between 10 and 25 °C, protected from moisture; maximum shelf life 6 months from manufacture in the original packaging under suitable conditions.
- 8W: store dry, above 0 °C and protected from moisture; shelf life 6 months in sealed drums; once partly used, reseal tightly and use promptly.
Equipment cleaning
A plasticiser-based cleaning fluid such as Rayston Fluid is recommended; using solvents to clean machine parts is discouraged. Remove component B from any parts exposed to air and replace it with cleaning fluid to avoid contaminating the next system.
Environment and empty containers
Treat empty containers as hazardous waste and hand them over to a licensed waste manager. A and B can be mixed 1/1 to obtain an inert material, in quantities not exceeding 5 litres, to avoid a dangerous build-up of heat.
11
Spray polyurethane foam FAQ
What is spray polyurethane foam, in short?
An insulation system formed on site by spraying two components that react to create a continuous polyurethane foam on the substrate — here, the Rayston Spray Foam product family from Krypton Chemical.
Do all Rayston grades have a similar density?
No. Applied density ranges from 8–10 kg/m³ for 8W to about 48–56 kg/m³ for 50W and 48–55 kg/m³ for HFO 50, with intermediate grades in between according to the datasheets.
What is the difference between 30W, 40W and 50W?
All three are rigid and water-blown. They differ mainly in applied density (28–35 / 38–42 / 48–56), λ (0.031 / 0.031 / 0.030), μ (≥60 / ≥70 / ≥70) and declared closed-cell content; of the three, only 50W declares a numerical compressive strength.
When should I choose HFO over W?
When the project needs the properties of the HFO range as stated in the datasheets: HFO/HCFO blowing agent, closed cells > 90%, a lower declared λ (0.028 or 0.021 depending on the grade) and a higher μ (≥ 80).
Is spray foam suitable for permanent loads?
The rigid-grade datasheets specify application on surfaces not subject to permanent loads (typically vertical walls and interior ceilings). Do not extend this to structural uses that are not stated.
Can it be applied as a DIY job?
No. The rigid-grade datasheets state that the product is for industrial/professional use and is not suitable for DIY.
Which reaction-to-fire class is declared?
Class E for the rigid grades listed (for all thicknesses, according to the technical datasheets). 8W states Euroclass F to EN 13501-1:2007.
Where can I find the thickness vs R-value tables?
In each grade’s technical datasheet (performance tables). This article summarises the comparison and does not replace the full table for the grade you select.
12
Grades — spray polyurethane foam articles by grade
A detailed article for each grade: Spray foam 8W · Spray foam 30W · Spray foam 40W · Spray foam 50W · Spray foam HFO 35 · Spray foam HFO 40 · Spray foam HFO 50.
8W
Rayston Spray Foam 8W
Published Spray foam 8W
30W
Rayston Spray Foam 30W
Published Spray foam 30W
40W
Rayston Spray Foam 40W
Published Spray foam 40W
50W
Rayston Spray Foam 50W
Published Spray foam 50W
HFO 35
Rayston Spray Foam HFO 35
Published Spray foam HFO 35
HFO 40
Rayston Spray Foam HFO 40
Published Spray foam HFO 40
HFO 50
Rayston Spray Foam HFO 50
Published Spray foam HFO 50
13
Engineering summary
Rayston spray polyurethane foam from Krypton Chemical covers a clear range: from a lightweight open-cell foam with declared acoustic performance (8W), to rigid water-blown grades (30W–50W), to HFO grades with a high closed-cell content and lower declared thermal conductivity (HFO 35 / 40 / 50). The right choice starts with the application question (thermal / acoustic / density / declared compressive strength) and is then confirmed with datasheet figures, not marketing generalisations.
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