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Using a hot water bottle cover has many advantages. While its most important function is to protect your skin from being in direct contact with the bottle, it also keeps your hot water bottle warm longer.
Hot water bottle covers come in different designs, some of them with fun patterns for children, and others with luxurious styles for those who like a fancy cover.
You might have noticed prices for these covers vary. Ever wondered why?
Simply because they are made of different materials, some higher quality than others. For example, a wool or cashmere hot water bottle cover will be far more expensive than a polyester one.
Let us explain to you why that is, and which material you should opt for when choosing your hot water bottle cover.
The best materials for your hot water bottle cover are polyester fleece and cashmere, followed by wool-acrylic blended, pure wool, and cotton. These types of materials have the highest insulating properties for your cover and will keep your hot water bottle warm for longer. The thickness of your hot water bottle cover is also an important factor: the thicker the material, the longer your hot water bottle will stay warm.
Most insulating types of material
Icewear, an Icelandic outdoor apparel and wool products retailer studied which materials were the warmest for clothing. More specifically, the study aimed at finding which fabric retained heat the most.
This is in direct correlation with our article, as we are seeking materials which will keep your hot water bottle as long as possible.
Below are the results of the study. Thermal conductivity (K) refers to how easily heat passes through the material. The lower the figure, the better the material retains heat and warmth.
Cashmere was not studied in Icewear's research. However, our own research led us to find cashmere is more isolating than wool, hence the shared first position with fleece. In addition, to the best of our knowledge, there is no data comparing polyester fleece and cashmere.
Ranking of warmest hot water bottle covers by material
Ranking | Material | Thermal conductivity |
1 | Polyester fleece | K=0.034 |
~ | Cashmere | Not studied, ranking based on other articles |
2 | Wool + Acrylic | K=0.035 |
3 | Wool (100%) | K= 0,039 |
4 | Cotton (100%) | K=0.040 |
5 | Polyester (100%) | K=0.050 |
6 | Silk | K=0.066 |
7 | Cotton + Acrylic | K=0.072 |
8 | Viscose + Lycra | K=0.104 |
9 | Cotton + Polyester | K=0.120 |
Which hot water bottle covers feel the best?
Now that we know which material is the warmest, which one feels best? This is of course very subjective and varies from one person to the next. Based on our experience, hot water bottle covers made of fleece or cashmere are the softest and thus the cosiest to snuggle up with.
To give yourself an idea, consider how comfortable you are wearing a wool sweater, over a fleece, cashmere, or cotton one. The feeling will be similar on your hands and body when using your hot water bottle.
Which materials are most expensive for a hot water bottle cover?
The most expensive hot water bottle covers you can buy are made of cashmere. The price for hot water bottle covers made of cashmere usually ranges between 100 and 200 euros (including the hot water bottle), depending on the brand and type of knitting.
Pure wool hot water bottle covers are considerably cheaper, with prices ranging between 30 and 50 euros (also including the hot water bottle).
Fleece hot water bottle covers are even cheaper and available for as low as 10 euros, including the hot water bottle.
The table below presents the most common materials used for hot water bottle covers on the market, ranked by warmth. As you can see, the most expensive option is not always the warmest.
Ranking | Material | Price range (incl. bottle) |
1 | Fleece | 10 - 15 euros |
2 | Cashmere | 100 - 200 euros |
3 | Wool | 30 - 50 euros |
4 | Cotton | 20 - 30 euros |
The importance of material thickness
Beyond the type of material you opt for, the thickness of the hot water bottle cover also plays a large role in keeping the heat in.
The thicker the material, the longer it will stay warm.
Similar to like jacket work, the trick is to keep a fine layer of air between the hot water bottle and the cover around it: you want to trap the hot air coming from the hot water bottle. This is why your cover shouldn't be too tightly wrapped around your bottle.
Should you use two covers for your hot water bottle?
Using a second layer over your hot water bottle may also contribute to keeping it warmer. However, this may trap too much heat and reduce the feeling of warmth you want to experience.
Feel free to experiment and wrap a thin layer around your hot water bottle (wrap it in a thin kitchen cloth first for example) before adding the actual cover made of wool, cotton, polyester or whichever material you opted for.
If it's not warm enough with two layers, just stick to using one! This provides enough protection for your skin and will be safe for use too.
Final thoughts
We hope this article will make it easier for you to pick the hot water bottle cover you need. Regardless of the material, you opt for or its thickness, the most important takeaway here is you should use a hot water bottle cover at all times, primarily to protect your skin.
Hot water bottles also bring the advantage of keeping it warmer longer, which is of course what most of us prefer too, especially in cold winter times.
Keep warm and cosy!
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