Hi Elise,
There are only 3 types of foam that are used in mattresses. These are latex, memory foam, and polyfoam. While they go by many many different names … all “foam” no matter what it may be called is one of these three.
Latex foam in its softer versions is a very good choice for comfort layers as it is very pressure relieving.
In its firmer versions … latex also makes an ideal support layer because it can “hold up” the heavier parts of the body and can support a wide range of differing sleeping positions.
While it is the most expensive foam … it is also the most durable.
Memory foam is all “soft” foam (even if it feels firm when it is cold or pressed down quickly) and non supportive (no matter how many claims to the contrary you may hear) so can only be used for pressure relief in the comfort layers (which it also does very well). All memory foam must have a firmer supportive material underneath it. There are no “all memory foam” mattresses sold commercially for this reason.
Polyfoam has a wide variety of different grades or qualities but in the grades that are usually used in comfort layers by most larger manufacturers in one sided mattresses it should be either avoided completely or minimized (no more than an inch) as it can break down relatively quickly when used in this layer. In the case of smaller independent manufacturers you may find higher grades that can be much more durable. In the support layers where it is not compressed as often or to the same degree … the higher grades used here are a good choice for more inexpensive mattresses where higher quality latex foam would put the mattress out of someone’s budget. 1.8 lbs is normally the lowest that should be considered but higher density is both more durable and does a better job in terms of performance. In Tempurpedic mattresses for example (and most memory foam mattresses), they use polyfoam under the memory foam for support. Many budget memory foam mattresses use 1.5 - 1.8 lb polyfoam for support while higher quality memory foam mattresses use higher grade polyfoam with a higher density. Latex is higher quality than any polyfoam.
The first step in choosing a mattress is to decide the overall type of materials and construction you want.
In the comfort layers you will be mainly choosing between memory foam and latex (polyfoam should only be a consideration in the lowest cost mattresses or in higher grades or better designs that are more durable). Lie on mattresses that have one or the other in the top few inches and see which overall feel you prefer. These two articles about the pros and cons of memory foam and the pros and cons of latex may help in your decision.
In the support layers you will be primarily be choosing between foam (either polyfoam or latex foam) or innersprings. Since you have already decided for foam … then the only real choice would be based on budget with polyfoam being used in a lower budget choice and latex foam in a higher budget choice.
The best way to test a mattress is to test different comfort layers for pressure relief (paying particular attention to pressure in your hips, pelvic crest, shoulders, and any other sensitive areas depending on sleeping positions) and to test the support layers for alignment (paying particular attention to any strain in the lower or upper back, that the hips aren’t sinking in too far, and that the shoulders are sinking in enough).
Some general guidelines about layering and layer thickness are in post #4 here and this section of the site.
Some guidelines about some of the more common traps and pitfalls in mattress shopping and better places to buy a mattress are in this article and in this article.
I’ll take a look at local factory direct outlets and/or better retail outlets in your area that I know about and post them here in a little bit (need to get a little caught up first :))
Phoenix