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Why Is My Bathtub So Cold? 4 Key Causes & Solutions


Why bathtubs are cold and how to solve it.

There’s nothing worse than climbing into a bathtub to find that the water isn’t warm enough. If you’re a fan of long baths, you might find it challenging to keep the water hot for the duration of your bath. 

Your bathtub may be cold for several reasons: poor insulation of the tub, inadequate insulation in the walls, a water heater that is too small, and a chilly bathroom. You could consider stone, copper, or acrylic materials for a warmer bathtub. Tub stones can also help.

In this article, you will find advice on how to keep your bathtub warmer, how to insulate the tub and the bathroom, and whether tankless heaters can solve your problem or not.

You’ll also find information on tub stones and how bubble baths can help keep your bathtub hotter for longer. I’ll also explain which bathtub materials work best for hotter baths, so read on.

Poor Insulation of the Tub

If your bathtub doesn’t have adequate insulation, you will lose heat quickly. Bathtubs lose warmth through their sides and bases, so insulating around and beneath the bath is essential.

Most bathtubs have at least one side next to a wall, but you can still insulate that side of the bath for maximum effect.

A freestanding tub has all its sides exposed, so it will need even more insulation within its walls.

Inadequate Wall Insulation

Bathtubs that lie alongside the house wall, especially an exterior wall, are likely to lose a lot of their heat through the wall. Consider insulating the walls around your bathtub.

Exterior wall insulation is even more important as your outer walls get much colder than your interior walls.

Freestanding tubs can benefit from wall insulation, too, as the warmer your room is, the slower your bath water will cool down.

A Water Heater that is Too Small

Most water heaters are an adequate size for the bathtubs and other items you want to fill. However, if you’re always running out of hot water, then your water heater might be too small for your tub. 

If you’ve replaced your bathtub, the new tub might be a lot larger than the old one, and your old water heater can no longer keep up. Whirlpool baths are unusually large and require large water heaters or tankless water heaters. A tankless water heater provides you with unlimited hot water.

A Chilly Bathroom

Bathrooms are full of hard, cold surfaces, like metal, ceramic, and glass. The hot water in your bathtub evaporates into water vapor, carried around by air, and then all those hard materials help the vapor cool faster. It then condenses back into a liquid. 

This process takes the heat out of the air, and any warm surfaces, like your hot water or warm body, and cools it.

Having a chilly bathroom is going to make your bathwater cool much quicker.

How Do I Keep My Bathtub Warmer?

The good news is, there are several ways to keep your bathtub hotter for longer. These methods include:

  • Insulating the walls
  • Insulating the bathtub
  • Refilling with hot water
  • Installing a tankless heater
  • Bathtub stones
  • Bubble baths

Insulate the Walls

If your bathroom walls have poor insulation, your bath water will cool down quickly, especially if the bath lies alongside an outer wall. However, insulating your exterior walls can be expensive and messy.

If this isn’t something you want to get into, consider insulating the tub instead, particularly the side, or end, that’s lying against an outer wall. 

Nevertheless, if cold baths are a frequent problem for you, you may want to consider insulating your walls, as well as your water heater or tank.

Insulate Your Bathtub

You can insulate a bath in a similar way to insulating a wall. Remove the panels, and coat the walls of the tub with spray foam.

It’s also possible to insulate underneath a tub to further decrease heat loss. There are some key points to know about doing this, however. Be sure to read Can Expanding Foam Be Used Under a Bathtub? Uses & Concerns

You can also fill in any gaps between the walls and the panels with Great Stuff Insulating Foam SealantOpens in a new tab. (link to Amazon).

If you really want to get serious about this you can spray foam insulation into your exterior walls.

You can find an excellent video on installing foam insulation by Home Improvements here:

How to Install Spray Foam Insulation DIY

Keep Refilling With Hot Water

If you have limitless hot water, topping up your bath with fresh hot water should be easy. However, most water heaters need time to heat a tank of water, and you may find you run out of warm water eventually. 

Baths are notoriously bad for the environment, and using too much water can also be expensive. You may also want to watch your water use in the summer, especially if there are local water restrictions or if you use a water meter to pay your bill. 

Usually, the water heater installed in your home is adequate for the bathtub. However, if you have installed a new bathtub in a larger size or different shape, you may find that your water heater is not big enough to fill it. Whirlpool baths, in particular, require much larger water heaters.

Install a Tankless Heater

If you have a large bath or use a lot of hot water, a tankless heater could be worth the money. You can even install more than one if you use a washing machine, a dishwasher, and a shower several times a day.

If you have a whirlpool or other large bath, installing a tankless water heater might be your best option.

Tankless water heaters are more energy-efficient and can save you money. Plus, they provide you with unlimited hot water.

Bathtub Stones

Bathtub stones, or tub stones, are devices that look a lot like natural pebbles. The tub stones will recognize your bath’s temperature and heat up when the water cools past a specific temperature. That way, you can maintain hotter water for longer.

Which Type of Bathtub Is Best for Keeping Bathwater Warm?

Acrylic, metal, or stone are the best materials for keeping your bathtub warm. Acrylic bathtubs with adequate insulation work well, and they are also reasonably priced.

Metal and stone are excellent conductors of heatOpens in a new tab., and with so much heat trapped in the bathtub for more extended periods, your water stays hotter too. The downside of stone or metal baths, though, is the high cost.

Why Is My Bathroom So Cold?

The bathroom is always the coldest room in the house, but there are several reasons why. For example, we usually don’t have clothes on in the bathroom, and since we’re almost always dressed, we’ve gotten used to those extra layers. 

Also, bathrooms are full of hard, reflective surfaces made of materials that always feel cold. The rest of the house contains soft furnishings and comfortable spaces. Even the kitchen, which probably has a tiled floor, is usually full of heat from cooking. 

Hard surfaces in your bathroom increase evaporation, which transfers heat from surfaces, and even your body, into the air. As your bathroom will have a fan, the warm air is quickly moved away from you, taking your body heat with it. Thus, your body temperature will drop quite quickly once you get out of the hot water. 

How Do I Make My Bathroom Warmer?

Another excellent way to improve your bath time experience is to make your bathroom warmer. There’s nothing worse than sitting in a hot bathtub in a chilly room. You can warm up your bathroom in several ways, such as:

  • Turning the radiator up
  • Closing the door
  • Putting thermal blinds or curtains up
  • Closing the curtains or blinds
  • Covering the floor with a fluffy bath mat

You can also preheat towels or pajamas for an extra special warming effect, using your radiator or a towel warmer. The Keenray Bucket Style Towel WarmerOpens in a new tab. (link to Amazon) comes in several colors and fits two large towels or even bathrobes. It only takes a minute to heat up, and will have your towels thoroughly warmed in six minutes.

If you can set one up far enough away from the water to be safe, consider getting a space heater. However, this is not recommended for small bathrooms or people who splash water a lot, like your kids. 

Conclusion

My wife has complained about our bathtub being cold for a couple of years now. I really wanted to find an easy solution but for us, it’s going to come down to either insulating the walls of the tub, using a dedicated tankless water heater, or both.

Your solution may be simpler. I suggest trying the easier, less expensive solutions first. Then progress to the more complex ones. That’s what I’ve done and ultimately, sadly, those simpler solutions didn’t solve the issue.

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Paul

As a homeowner, I am constantly experimenting with making the structure of my house more energy-efficient, eliminating pests, and taking on DIY home improvement projects. Over the past two decades, my family has rehabbed houses and contracted new home builds and I've learned a lot along the way. I share my hard-learned lessons so that you can save time and money by not repeating my mistakes.

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