Memory foam sells mattresses, so people assume it must be the premium choice for a sofa or a chair. In seating, it is usually the wrong one. Here is how memory foam and high-resilience (HR) foam actually behave under a sitting body, and where each belongs.
What the two foams are
High-resilience foam
HR foam is a polyurethane foam with a more open, irregular cell structure than standard foam. It compresses easily on first contact and then pushes back progressively – the “support factor” is high, which is the technical way of saying it feels soft to sit down on but doesn’t bottom out. It recovers its shape instantly. HR35 (35 kg/m³) is the NZ workshop standard for seats; our HR35 sheet is the one we cut most.
Memory foam
Memory foam, or viscoelastic foam, is polyurethane with added compounds that make it temperature-sensitive and slow to recover. It softens where it is warm, moulds to the body and returns to shape over several seconds. Densities are typically 40–80 kg/m³ – higher than HR – which is why it is often marketed as “higher quality”. Density in memory foam measures the amount of material, not durability in the same way as for HR foam.
Memory foam vs HR foam: the comparison
| Property | Memory foam | High-resilience foam |
|---|---|---|
| Feel on sitting | Sinks slowly, cradles | Springy, supportive |
| Recovery | Slow (3–10 seconds) | Instant |
| Temperature sensitivity | Firm when cold, soft when warm | Stable across temperatures |
| Heat retention | High – sleeps and sits warm | Low – breathes |
| Ease of standing up | Harder – you are ‘in’ the seat | Easy |
| Durability in seating | Loses recovery in 3–6 years of daily use | 10–15 years at 35 kg/m³ |
| Edge support | Poor on its own | Good |
| Weight | Heavy | Moderate |
| Cost | Higher | Moderate |
| Best use | Toppers, pressure relief, bed surfaces | Sofa seats, chairs, benches, van beds |
Why memory foam struggles in a sofa
Sitting is not lying down. Your weight is concentrated on a small area, you move constantly, and you get up and sit down dozens of times a day. Memory foam’s slow recovery means it is still recovering from the last sit when you land again; over time the cells fatigue and the “memory” becomes a permanent dent. It also has almost no edge support, so the front of a cushion collapses and you slide forward.
Then there’s temperature. In an unheated NZ lounge in July, a memory-foam cushion is a brick until it warms up; in February it is a warm marshmallow. HR foam feels the same year-round.
Finally, memory foam holds heat. On a mattress with a breathable cover that is tolerable; under a tight vinyl or leather seat cover it becomes sweaty within minutes.
Where memory foam genuinely helps
- Pressure relief: wheelchair cushions, hospital seating, people who sit for many hours with limited movement. Here the cradling effect is the point.
- Toppers: a 25 mm memory layer laminated over 75–100 mm of HR35 gives a soft, contouring first touch with proper support underneath. This is a good combination for a recliner, a day bed or a campervan bed.
- Mattresses and sofa-bed mattresses: as a top layer over HR foam for guests who sleep on it.
- Headrests and neck rolls: where slow contouring is comfortable and load is tiny.
Where HR foam is the right answer
- Loose sofa and armchair seat cushions – 100 mm HR35
- Fixed seats on springs or webbing – 50–75 mm HR35
- Dining chairs, bar stools and benches – firm HR35
- Office and desk chairs – HR35 or a firmer HR grade
- Boat and van seating – HR35 in dry areas, dry-fast foam where wet
- Ottomans and footstools
If you want more softness than plain HR35, laminate a softer 25 mm layer on top rather than switching to memory foam. See our foam thickness guide for layering by furniture type.
Latex and gel foams
Two other options come up in the same conversation. Natural or synthetic latex foam is springy like HR, breathes well and lasts a very long time, but it is heavy, expensive and rare in NZ upholstery sizes. Gel-infused memory foam addresses the heat problem of standard memory foam by adding gel particles or a gel layer; it helps on a mattress, but under a seat cover the improvement is small and the durability issue remains. For seating, both are answers to a question HR35 already solves.
Reading the labels
Suppliers describe foam with a density and a hardness figure. For HR foam, density (kg/m³) is a good proxy for lifespan: 35 kg/m³ is the daily-use benchmark and 40+ is heavy-duty. Hardness is given as ILD or in kPa; a firmer number suits smaller seats and heavier sitters. Memory foam is sold mostly on density and “feel”; a lower-density memory foam (under 50 kg/m³) breaks down quickly and should be avoided even as a topper. Our guide Foam density and firmness explained walks through the numbers.
Cost over the life of the piece
Memory foam usually costs more per sheet and lasts less time in a seat, so the maths is straightforward. A 100 mm HR35 sofa cushion that lasts 12 years is cheaper per year than a memory-foam one that needs replacing after five, even if the memory foam felt nicer in the first month. Spend the extra on a good Dacron wrap and a better cover fabric instead.
Our recommendation
For anything you sit on: HR35, with a soft top layer if you want plushness. For anything you lie on for long periods, or where pressure relief matters: a memory-foam layer over an HR core. For hot climates, vinyl or leather covers and boats: HR only.
If your seats have gone flat and you are in Auckland, our sister workshop Upholstery World replaces foam and can advise on the combination for your frame. For the DIY route, send your cushion sizes through our contact page and we’ll cut and laminate to order.
Shop it: Choose foam that lasts. Order HR35 high-resilience seat foam in 25–100 mm sheets or cut to size, plus Dacron wrap, from our foam & padding range. Everything ships nationwide from our workshop — courier to any New Zealand address, or click & collect.