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Best Coffee Mug Testing & Lessons for Builders

What does a good coffee mug have in common with a good house?  I am a fan of both Good Coffee, and of course a well built home.  So bear with me here as I ran an experiment in my kitchen on a rainy Sunday afternoon to see which of my mugs will hold HOT coffee the longest.  I was introducing my 8 & 10 year old kids to Monopoly so this gave us something to do while we played a 4 hour board game!

Here’s the contenders that I had in my cupboard.  I wanted to get a mix of what I thought were “Standard” mug as well as my three usual coffee to-go mugs.  First, I used the heavy ceramic mug as my control.  Next I pulled out a small Tervis brand tumbler which is a double wall plastic mug (White Stars), then my wife’s Tea mug (pink stripes) which is double wall ceramic, then three of my favorite coffee mugs.  The Black Zojirushi 16 oz Metal Double Wall, the White Kleen Kanteen 12 oz double wall metal, then a Yeti Rambler 20 oz Metal double wall.


The field of contenders from my cupboard: Heavy Ceramic Mug, Tervis Double Wall Plastic, Ceramic Double Wall, Zojirushi Metal Double Wall , White Metal Kleen Kanteen Double Wall, Yeti Metal Double Wall
The field of contenders from my cupboard: Heavy Ceramic Mug, Tervis Double Wall Plastic, Ceramic Double Wall, Zojirushi Metal Double Wall , White Metal Kleen Kanteen Double Wall, Yeti Metal Double Wall

I started with 200 degree water from my Cuisinart Tea Kettle (verified with my Thermapen thermometer) and poured exactly 1 cup of hot water into each of the mugs then put their caps on (all except for the open top ceramic Control Mug).  



I put the mating lid on each mug after filling with 1 cup of 200 F water.
My two oldest kids helped me measure and chart this Sunday experiment.

We took measurements from each mug at 15 minute increments, but kept the lids on/closed except when taking a temperature reading.

Table Mug Performance


Here’s the table we created.  I like my coffee hot and through some experimentation realized that 140 F is my threshold where I still mentally feel like the coffee is “hot”.  The results are pretty interesting with the first three mugs not making it past 30 minutes (as I suspected).  But, I was surprised by my three favorite mugs.  All three metal double wall mugs seem to be made from similar materials/thicknesses, but for some reason I expected the results to be closer than the actual performances turned out to be.  I think the real difference between these mugs is the lid.  The “insulation” system of the walls appears to be similar, but the lids are vastly different.  The Yeti mug has an open hole on top so all you need to do is tip it back and start drinking.

Yeti Mug is one of my favorites for daily drinking as there is not lid to take off when you want to drink.

The white Kleen Kanteen mug has a turnable cover over the hole but doesn’t appear to provide any insulation.  It will also spill if tipped over, so I don’t consider it to be air tight either.

The Kleen Kanteen mug topper rotates so it can be “shut” though it’s not spill-proof.
The Zojirushi mug has a nice rubber gasket that make it spill-proof and therefore air-tight too.
The Zojirushi mug has a nice rubber gasket that make it spill-proof and therefore air-tight too.

And finally here’s a closeup of the lid for the winning Black Zojirushi mug.  The latch makes the rubber gasket seal tight against the plastic spout and works really well.  Though it is annoying to constantly flip open, the results speak for themselves.   After many hours it was still well above my 140 F threshold of hot coffee.

Ok, so how can we extrapolate this to houses?  I’m taking some liberties here, but I think the “Control” mug is how most American homes have been built in the last 30 years.  They can barely hold their temperature on a “hot” day without intervention of the HVAC system.  On a normal Texas summer day I suspect most homes can barely go 15 minutes in the middle of the day without needing the AC to kick on and cool the house.

Meanwhile, the Kleen Kanteen & Yeti mugs have some pretty darn good “insulation”.  There are no Thermal Bridges in these mugs with the double wall stainless construction.  My hand doesn’t feel the 200 degree water inside the mug even though it’s millimeters away.  Same killer insulation with the Zojirushi mug.  But, the difference is Air Sealing!

The Black winning mug seals tightly and the other two do not.  I think this is pointing out a key flaw in High Performance homes built in this Country.  We have some darn good insulation systems, but we need to pay attention to our air sealing.  We should be installing top performing windows/doors, doing the best air sealing we can, and letting our killer insulation systems do the work they are intended to do!  Funny how I sound like a Passive House guy all the sudden.

Marvin Exterior door has multi-point locks & dual gaskets to seal tightly!
A bank of Marvin Casements & Fixed windows certainly helped me get my lowest blower door score ever on this house!
IMG_8933 - Version 3
Applying primer to this wall so the peel & stick Delta Vent SA will stick tenaciously. Notice the sticky strip on top of the Delta so the overlap even double sticks!

Here’s two take aways from this experiment:

  1.  Use the best air sealing method possible as you never get a second chance at doing this once the house is completed.  I’m building a SIPs house now and this week I’ll be wrapping the entire envelope with Cosella Dorkin’s Delta Vent SA (a vapor permeable peel&stick housewrap).  Peel & Stick products are terrific for air tightness as they are fully adhered the outside of the house.  Let the Structural Insulated Panel insulate, but be sure not to negate the killer insulation by leaking in energy robbing air.
  2.  Where you do have “holes” in your envelope be sure you have a good air sealing product to plug that hole.  A standard lumberyard door is a pretty air leaky opening in the envelope, but a Marvin door has a multi-point locking system with two gaskets to seal.  Same with Marvin Windows, the double gaskets I see on their windows are terrific at air sealing compared to a standard window.  I’m also a big fan of Casement windows in general because of the lock pulling the window into the gasket for further air-tightness.  The pictures above are from a house my company built with all Marvin Windows/Doors and it set my company’s record for tightest house built.  The “Cap” on the coffee mug really does make a difference!

Ok, well enough coffee talk.  Time for me to get out to the field and #build some Insulated & Air Tight houses!


-Matt Risinger

Risinger Homes in Austin, TX

Visit my Blog at www.MattRisinger.com

Risinger Homes is a custom builder and whole house remodeling contractor that specializes in Architect driven and fine craftsmanship work. We utilize an in-house carpentry staff and the latest building science research to build dramatically more efficient, healthy and durable homes.

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