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Rebuilding a Mattress: Have a few questions (UPDATED 5/17/19)

31 May 2019 22:49 #11 by Phoenix
Hi androiddd,

have a 5 inch base of HD 36 poly foam. I'm starting to wonder if that's too thin. It's not quite as stiff as it was when I purchased it several years ago. I may try swapping another similar piece from a bed that never gets used. Or I could throw both pieces on, and have a 10 inch base. What you think about that?”

You can certainly use another piece of 5” HD polyfoam. I would put the lesser used foam on the bottom as the one you were sleeping on now is probably a little softer than when you first purchased it. Not sure it will make a tremendous amount of difference in feel except for a height that you may be more comfortable with.

Generally speaking, latex is more breathable than memory foam and many people use the latex above the memory foam because it is much more temperature neutral than memory foam which tends to sleep hot. It's difficult to compare as each individual has different preferences...Dunlop has a different "feel" and performance than Talalay and is less lively or springy. You can see a comparison between them in  post #7 here   but your own experience is really the only way to know which one you prefer with any certainty. Some people would notice more of a difference than others with transition or support layers that used each material if the top layers were the same type of latex because you will "feel" more of the upper layers than the deeper layers ... at least when you first lie on a mattress. Dunlop always has a bit firmer feel than Talalay latex.

“If I replaced it with a firmer piece, what would be the appropriate ILD?”

If you replace the Dunlop topper with a firmer feel you may want to try a 28-32 ILD. The latex will give you longer durability than most memory foam toppers. Especially a 3-pound memory foam topper. As you have correctly pointed out … low-quality memory foam will breakdown quite quickly, thus after a short time your mattress will feel completely different than when you first purchased it.

One thing I did discover in all this experimentation is that putting a mattress pad on top of memory foam totally changes the firmness of it. Previously I had just a thin sheet-like cover, and that meant we sunk into the memory foam. A relatively cheap mattress pad means that you sink less into it.

You are making a good point! It is always interesting to see how the smallest change can alter the feel of the sleeping system because every layer and component in a mattress can affect the feel and performance of every other layer and the mattress "as a whole" ... the most reliable way to know if this is a good match for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) is of course based on your own careful testing of how much the mattress pad itself can change the firmness of the mattress. This is also another reason why people can’t do DIY layers and then try to match up the mattress with the comfort layers one got used to as it always feels completely different when a manufacturer finishes a mattress.

Another issue is temperature. I find that memory foam sleeps hot. Would buying and using a wool mattress pad lower the temperature? Or should I consider another solution such as a 1 inch layer of latex on top of the memory foam?

The wool will help with wicking away moisture but It's not really possible to quantify the sleeping temperature of a mattress for any particular person with any real accuracy because there are so many variables involved including the type of mattress protector and the sheets and bedding that you use (which in many cases can have just as significant an effect on sleeping temperature as the type of foam in a mattress) and on where you are in the "oven to iceberg" range and because there is no standardized testing for temperature regulation with different combinations of materials ... there is more about the many variables that can affect the sleeping temperature of a mattress or sleeping system in post #2 here that can help you choose the types of materials and components that are most likely to keep you in a comfortable temperature range.

Now I see why people just buy a mattress online or in a store. Tweaking mattress, especially as the layers wear out, is tricky.

I think you put it very simply but the DIY is ok for some people, of course even mattresses not DIY, and made with mediocre materials, and lower densities will wear out quickly also, so the same issue can exist with the traditional mattress purchasing.

Finally, as I consider replacing the memory foam, I'm debating whether or not to use 5 pound memory foam or 4 pound memory foam? From what I understand, the higher density memory foam will be more enveloping, whereas the lower density may be more resilient, and perhaps the higher density will last longer. I do know that my last experiment using 3 pound memory foam lasted a very short time.

I think you are on the right track with the 4lb and 5lb in terms of durability. I am not sure if you have read the durability guidelines as this article points out some o the issues with lower density memory foam, and also discusses regular polyfoam. While you are correct that the higher density will last longer it is the IFD of the memory foam that will give it the “enveloping” feel that you are describing regardless of the density of the memory foam.

From what I understand, the higher density memory foam will be more enveloping, whereas the lower density may be more resilient...

If anything, memory foam is better described as a "dead feeling" foam as it absorbs energy that is applied to it and it has little to no “resilience” as opposed to latex, polyurethane, inner springs, or even many natural fibers so … it is not nearly as springy or lively. It responds very slowly to new and changing positions like "sleeping in the sand"

I hope this helps and let us know if you have any other questions.


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