Question for Phoenix about Costco Beds

I have read much of your website and first, thank you SOOOO much for all of the information, it has been many hours of reading and a great education. My husband and I are prepared to head to the bay area to some of your recommended manufacturers to check out beds, however, I need your honest opinion on the new beds at Costco.
We have our own full-time business and realize the time we have invested and will still need to invest to do this is costing us a lot and so I am coming to you as the expert.

I feel if I can test the Costco beds and get an “initial” feel and if you think they are durable and after what I have read from your site they do pass the “minimum” standards – then we may have to go that route – return policy sure helps

We are willing to spend the little extra because of the return policy in this case.

Are needs are the “coolness” and “durability” of course
We are looking at the Sleep Science Black Diamond and the Cool Gel bed – not sure if the Black Diamond layers will offer the “cool” effect with the bamboo – that is not something that I found on your site or theirs – your insight would be helpful there. We are looking at the 11" thicker bed and we are looking at the split king or xl-twins (one factor is the weight of a single king)

Your comments and suggestions would be greatly appreciated.

Many thanks in advance – an admiring fan of your site – and again, THANK YOU for all of the time and effort you have spent putting your site together.

Hi cherlyz,

You can read some of my thoughts about buying from Costco or other big box stores in post #4 here. In some cases they have some good quality/value available but because they are not “mattress people” they are not able to really provide any guidance about the suitability of any of their mattress for specific body types or sleeping styles so you would really be depending on their return policy and getting a free roll of the dice. If you are able to test a mattress in person of course and you do some careful and objective testing then the risk of making an unsuitable choice in terms of PPP (Posture and alignment, pressure relief, and Personal preferences) is much lower and then the only consideration would be making sure that the quality of the materials and value is good compared to other options you have available. If you are looking at memory foam options then there are also some good online memory foam choices listed in the links inside the “read first” post (post #1 here in case you haven’t read it) which also offer free returns in case you make a choice that is less than ideal.

While I can’t speak to whether a mattress is suitable for your need and preferences (see post #2 here) … I can certainly share my thoughts about quality or value.

Sleep Science Black Diamond:

You can see my thoughts about this mattress in post #4 here.

Sleep Science Cool Retreat 11" Gel:

This mattress uses 4" of 4 lb memory foam (a 2" layer with “gel inserts” and another 2" layer without) so the quality / density of the foam in the top 4" comfort layers are a little lower than the Black Diamond. I would also guess that the polyfoam support layers are also 1.8 lbs or above which would be suitable. They don’t say the thickness of the gel inlay in the top layer but solid gel is a high quality, durable, and “safe” material (see post #4 here). My biggest concern with this mattress … like the Black Diamond … is that Sleep Science / Southbay doesn’t have any certification for harmful compounds or VOC’s for the memory foam and polyfoam in their mattress (I would not be concerned with the latex or the gel inlay). Overall the quality/durability of this mattress in the comfort layers would likely be a little lower than the Black Diamond because the top 4" uses lower density or less durable materials than the Black Diamond (other than the top gel layer) although the gel inlay would also increase the durability of the 4 lb memory foam below it.

In terms of temperature regulation … there are many factors that combine together that affect the sleeping temperature of a mattress and you can read more about them in post #2 here and the links to other posts and information it includes. One of these links talks about the three different “technologies” that are used to regulate temperature (thermal conductive materials, phase change materials, and moisture wicking/ventilation). Phase change and thermal conductive materials tend to have a more temporary short term effect on the sleeping temperature of a mattress and once temperatures have equalized then the foam itself becomes an insulator. The most effective temperature regulating technology over the course of the night is moisture wicking and ventilation.

While there is no way to quantify the specific sleeping temperature of one mattress compared to another outside of your own personal experience … the Black Diamond has less memory foam in the comfort layers and has more elastic and breathable latex underneath which means that you would likely sink in less which would be “cooler” in theory than the same thickness of memory foam. On the other hand … the Cool Retreat has more memory foam that is lower density so you would sink in more deeply into the insulating memory foam but this would be offset to some degree by the gel inlay (at least temporarily while you are going to sleep if not over the course of the whole night) and the memory foam is a little lower density which is generally more breathable than higher density memory foam. The Black Diamond uses a silk blend for their mattress cover (but they don’t mention what it is blended with or the amount of silk in the blend which could be very low) and the Cool Retreat uses a polyester/nylon blend so I would give the cooling edge in terms of the cover material to the Black Diamond because of the cooling properties of natural fibers like silk.

In essence … both of these are memory foam mattresses so they wouldn’t be as temperature regulating as latex or natural fiber comfort layers and the other layers and components (such as your mattress protector, and your sheets) will also have a significant effect on the sleeping temperature regardless of the type of foams or materials used in the top layers of the mattress.

So hopefully this “analysis” will help you make some of the more intuitive or “best judgement” comparisons that can help you decide whether either is your best choice or help you choose between them based on your own personal value equation.


Great info as always, we are ready to contact our San Francisco manufacturers and “go testing”… as they are the closest to us.

Once again, MANY thanks for your time and the wealth of knowledge you have shared with us.