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Classic car storage in the UK.

I’ve owned and therefore stored classic cars here in Worcestershire for over 25 years and am often asked which method I find works best so I’ve decided to write up my thoughts.

The main enemy of course is water in its various forms. My cars include the Amphicar which (obviously) gets wet, sometimes inside as well as outside.

So, let’s start with rust, it’s the problem everyone thinks of first.

To rust (that is turn steel in in to ferrous oxide) the surface of the steel needs air and water. First step is to stop them reaching the steel, paint does that pretty well but even better is wax. I still prefer spirit based products such as Waxoyl or the similar “Mil Spec” from Rustbuster.co.uk. These work superbly, last for decades, and can be easily removed with white spirit for future welding or painting. However they can affect rubber parts so there I prefer “dry” wax such as Wurth cavity protection spray which comes in an (expensive) aerosol. The Wurth product is great for items such as the chrome bezels around gauges which have a rubber seal between them and the glass.

Chrome is worth a mention. It is surprisingly porous and normally underneath is steel so it needs protecting. A covering of wax, ordinary car wax (like Autoglym), will do and then looks invisible or for longer storage use a visible wax like Waxoyl. Chrome cleaner is generally abrasive and removes any wax coating, use it to clean but it doesn’t protect.

So, that covers the surfaces so to speak. To stop air, for things like spare bearings, keep them in airtight bags, smaller the better, buy freezer quality rather than general quality as they are thicker. The American Ziploc brand with Smartlok in Quart or Gallon sized are my favourites. They are now available in the UK on Ebay. No UK bag comes close in terms of quality of performance.

However you can’t put a car in a Ziploc bag (well in fact you can – more later) so let’s consider other options for stopping water from reaching and rusting steel. People get hung up about temperature and humidity and often talk about keeping humidity below 50% to stop rust but it’s more complicated than that and one of the keys is understanding about dew points.

All air contains water and as the temperature drops that water tries to change back from a vapour to a liquid, that’s what causes rain, warm moist air pushed up by the weather cools and the water in it becomes a liquid - rain. In the house you see it as condensation around bedroom windows on cold mornings. It is around the window because that is normally the coldest part of the room.

There are 3 ways to fix condensation:

1. Heat the room so the air inside can hold more water.

2. Open the window (ventilate) in the hope that air coming in from outside will be dryer and therefore hold more water.

3. Use a dehumidifier to reduce the percentage of water in the air.

Another way you can see this condensation effect is if you remove a can of cold soft drink from the fridge. Even in a warm house you immediately see condensation on the can as the water in the air rushes to the can and condenses back into a liquid.

And, that is what a dehumidifier does. There are a couple of different sorts of dehumidifier but the concept is simple, you present a cold surface to the air, the air gives up its water which is then collected in a container. The fan in a dehumidifier keeps an airflow over the cold surface so as much air as possible reaches the cold surface.

So, looking again at car storage.

Heating the space to about 20c works well (in fact any heat helps) because the higher the temperature the less the water has an affinity to condense back to a liquid.

It’s not the complete answer though, think of the condensation you get in a bathroom after a long hot shower even if the air temperature is 25 or even 30c. However if you heated a normal garage to 20c the car would sit in there and not deteriorate but even with insulation that is expensive, this is of course why US “dry State” cars are popular.

If you have a brick built garage insulate as much as possible. Try and get the walls cavity filled and insulate the doors with Kingspan or similar. If the roof is open fit a ceiling. You should then be able to keep that room at about 9c throughout the winter with no additional heating and that will be a big help.

Timber garages also have good insulation values but beware of metal garages (or garages with metal roofs). If the air inside is warm, say 15c, but the temperature drops overnight then that roof could drop to maybe 2 or 3c and then it’ll behave like the inside of a dehumidifier and droplets of rain form and it rains inside the garage. Insulating the roof with Kingspan can help.

Same thing can happen with any garage on a warm moist day, the air rushes in and condensation forms on whatever is coldest which is often the car.

This brings me to the issue I have with the Carcoon and similar “airflow” products. First I should say Carcoon is a trademark but has become a generic name. A similar product I have also used is the Airflow Airchamber. This looks like a framed version of the Carcoon and the idea is you can drive in and out but against that is takes more space.

A Carcoon can make sense and helps with the issue of mould that I’ll mention later but ONLY if the air that gets blown in has a higher dew point than the air coming out.

If a Carcoon is used inside then normally that’ll be the case. So for instance if you kept a car in a large closed modern building such as a warehouse on an industrial estate then a Carcoon can work really well, the airflow removes any residual water and stops moulds forming. If that environment is dusty the filters also keep the car clean. There is also a degree of security (unless the Carcoon is clear plastic).

However, if the building is an open barn or if the Carcoon is outside you have the issue with warmer moist air entering and then if the vehicle is cold the car itself will behave like a dehumidifier, the water will be drawn to it and condense, which is the worst possible situation. The Manufacturers claim that the airflow means this doesn’t happen, it does, I’ve seen it with one of my own Carcoons especially when used outside.

There are 2 more issues with the outdoor Carcoons, if it snows the snow does cause it to collapse (photo) and in wind it can rub on the paintwork, however if there is no other option the Carcoon is better than nothing and certainly better than a tight cover.

Yes, let’s mention the tight cover or rain cap. If you have a convertible with a leaky roof then they make some sense to keep the interior dry but the ones that cover the whole car cause sweating and mould inside. In theory some covers are breathable. I’ve tried a few and I’m not convinced, slightly better but still when you remove them the car is often wet.

I mentioned tent like covers as an alternative to a garage. Avoid the “gazebo” like products on Ebay, first gust of wind they crumble, some in the small print even say “do not leave up overnight” ! There is a quality brand called Dancover and also a new range of “portable garages” available from Machine Mart. Both are good and durable enough to last a few years but they can still have condensation issues in the winter as the plastic covering materials (and the metal poles) attract condensation.

I mentioned earlier about putting a car in a freezer bag – well there is a product that does exactly that, the Permabag from German company J F Stanley. I like this product and am currently using one. Simple idea, as the bag is sealed the humidity inside will stay constant – that is true but as explained earlier if the temperature of the air drops the water in it will still condense on whatever is coldest, normally bare metal, so the humidity needs to be maintained at a level such that dew point isn’t reached. Permabags come with a couple of canisters of “rechargeable” desiccant canisters. What is inside is a mystery, it looks a bit like china clay and is hydroscopic. Idea is it absorbs water and then you reheat in an oven to get the water out again. I haven’t had much luck with these. They do reduce humidity a bit but the recharging process doesn’t seem to make sense – or work – so I don’t use them. Instead I use a normal dehumidifier to reduce the humidity inside the Permabag and then seal it with a couple of calcium carbonate tablets inside to keep it low. That works well as long as it isn’t opened often.

Don’t go mad at removing humidity or leather and wood can crack. Permabag has a little window so you can see readings on a humidity meter inside.

One downside of Permabag is that if there is fuel in the tank a strong smell of petrol can build up inside and get “impregnated” in the interior so it works best if fuel is drained. Also lead acid car batteries give off a corrosive gas (can’t remember which one) so always remove the battery as well.

The Permabag has one other advantage, it keeps whatever is inside it dark and stops UV light which certainly helps rubber products, tyres of course but things like door seals as well last much longer and retain their original feel and structure. Plastic also doesn’t yellow if there is no UV.

So, for a car that isn’t used much, a Permabag is a good choice and as it can be no bigger than the car would be a great for long term storage in a UK domestic garage. Put valuable parts and tools inside the car so they benefit from the same environment.

For a classic car that is used then, insulate the garage as much as you can, keep it airtight and use an automatic dehumidifier set at 50 or 60%. Humidity meters are notoriously inaccurate so try a few or test to keep the balance right.

Simply using a car regularly is a great way to keep everything in good condition.

A garage will normally have a solid concrete floor. If this is less than 30 years old it should have a damp proof plastic membrane under the concrete. If it doesn’t or if that is damaged a dehumidifier will struggle as it will try to pull ground water up through the concrete.

So dehumidifiers, I mentioned before there are 2 different types, evaporation or conventional and desiccant. Desiccant is what you want in cold conditions. I can recommend a company called Dry-It-Out at dry-it-out.com they have a product called the ELA882 that I’ve found works very well. They aren’t super well built but are cheap and so far have been reliable. I have a couple here and have been running one in my garage for over 2 years. Running costs aren’t high, they take 28w all the time and when the dehumidifying part kicks in that increase to 800watt so about 10p an hour but that is only a few hours a day.

The convenience of being able to walk in to the garage (main garage is attached to my house) and see the car and get any tools is great.

Finally mould, I’ve had that a couple of times but always been my fault by ignoring some basic rules. It’s been on things like carpets and fabric seats that were not completely dry and then stored somewhere slightly humid and without airflow, in those condition the mould forms. Not too difficult to get rid of the mould spores, a soft brush will normally work, but watch out as they can make you cough badly if you breathe them in.

David Chapman Feb 2014. I’ll paste below some useful car storage info I’ve just found on the Dry-it-out website which I don’t think contradicts anything I’ve said above J

· All air contains a certain amount of moisture. The ratio of the amount of moisture in the air compared to the maximum that the air can hold at a given temperature is called the Relative Humidity or RH and is expressed as a percentage. For a given amount of moisture, the higher the air temperature the lower the RH%. Equally the lower the air temperature the higher the RH%.

· It is the cooling of air that causes the problems. As air cools it can hold less and less moisture until a point is reached where the air is fully saturated (100% RH) - known as the dew point. If the car, tools, or anything else in this environment, is at a temperature below the dew point of this air then moisture is given up by the air as condensation. This manifests itself as wet car surfaces, rust on tools, damp paperwork etc. Because the moisture condensed out from the air is pure distilled water it is also the ideal environment to encourage the growth of moulds and fungal spores.

· The solution to the problem is to reduce the dew point to a level below the temperature of any part of the garage and its contents AND to keep the RH% within controlled levels.

The aim is to arrive at a stable environment between 40% and 60% RH independent of outside temperature. Below 60% bare metal can be left out in the open and rust/corrosion all but stops. Below 40% RH leather and wood can dry too much and will become brittle and crack. This target environment can be achieved in several ways:

By heating the garage the air becomes warm enough to hold the moisture and condensation stops - well nearly stops - if you bring a cold car in from outside into a nice warm garage then condensation occurs immediately (like taking a milk bottle out of the fridge). Heating also has one other serious drawback - cost. To heat the average garage sufficiently will require several kW of power either as electric heaters or radiators. This heat will need to be continuously applied through cold weather to stop condensation and this will be very expensive to run.

This can take the form of natural ventilation built into the garage or forced ventilation by installation of a suitable extraction or positive pressure device. Ventilation will remove the stale high humidity air from the building at little or no cost. One current commercial system on the market incorporates a small heater to aim to lower the RH% of the incoming air. The reality of these systems is that the air that enters the building from outside to replace the exhausted air will still be high in humidity. Claims that for every 1 degree increase in temperature the RH% will reduce by 5% are frankly inaccurate, as the relationship between temperature and RH% is not constant. Furthermore, any temperature rise has to be sustainable throughout the whole of the garage volume - think how little a 3kW fan heater does to the garage temperature. There is no control over absolute humidity level in the garage - only of the air entering the garage. The average humidity level in the building can still remain above the point where deterioration can occur.

Several manufacturers supply systems that enclose the car completely in a plastic ‘bubble’ and provide low volume ventilation airflow that evens out the humidity within the bag and maintains its shape. These systems stop condensation quite successfully and are relatively cheap to run. The downside is that the systems make no attempt to control the RH%. The contents of the bubble can still be at a RH% well above safe levels. Another disadvantage is a practical one - these systems are fine if you want to move the car very infrequently. If you use, or work on, the car in the winter then getting it in and out of the bubble can be laborious and adds to the wear and tear of the bag itself. It is also obvious that only the air within the bubble is controlled - everything else within the garage area is unprotected - tools, stored parts etc.

By removing the moisture from the air in the garage with a car storage dehumidifier everything stored in the garage will remain condensation and corrosion free. Dehumidifiers are cheap to run, quiet in use and largely maintenance free. Suitably sized units will reduce and then maintain the humidity within the 40-60% RH target environment. In-built humidistats ensure that the air does not become too dry or too wet by turning the machines on and off as required. A correctly chosen dehumidifier will tolerate periodic changes of air such as opening the garage door or internal door. Furthermore, the action of dehumidification will bring the building as well as the contents into moisture equilibrium after a few weeks. If you then bring a wet car into the garage after a run in the rain it will actually dry it out for you!

· There are two main types of dehumidification equipment on the market - each use a different method to extract moisture from the air.

By far and away the most popular type of dehumidifier, certainly for domestic applications is the condensate type. A condensate dehumidifier uses the principle of dew-point to its advantage. Air is passed over a cold coil and is cooled to below dew point thus giving up its moisture as condensation on the coil. This condensation drips from the coil into a collecting tank below or is piped away to a drain. The dry air is then passed over a hot coil before exiting the unit. The air coming out of the dehumidifier is a degree or two warmer than that going in.Dehumidifiers

using this principle are small in dimensions and easy to install - just requiring a mains power point. If you want the water to drain away continuously then a pipe can be attached through a removable blanking plug on the machine. The machines require no regular maintenance other than periodic cleaning of the built-in air filter and can be expected to last for 10-15 years. All modern machines use CFC free refrigerants.

· A word of warning - Do not use standard domestic dehumidifiersin an unheated garage environment. They will not work when the ambient temperature drops below about 10C. The condensing coil becomes so cold that it freezes solid and the dehumidifier stops working. All the machines Dry-it-Out supply have 'Hot Gas Defrost'. Machines with Hot Gas Defrost detect the onset of freezing on the coil and either reverse the flow of refrigerant or vent warm air internally to automatically defrost the condensing coil. A dehumidifier with Hot Gas Defrost will operate at ambient temperatures right down to freezing point and most will stand -5C without machine damage.

To control the larger volumes of, for instance, a commercial car store, a different type of dehumidifier has traditionally been used - an adsorption dehumidifier. Adsorption dehumidifiers use a completely different principle to extract the moisture from the air.

· Air is passed through a high surface area rotor (rather like a catalytic converter to look at) that is impregnated with silica-gel. As the air passes through the rotor the moisture is adsorbed onto its surface. Part of the rotor is separated off from the main airflow. Through this part a small amount of air is ducted in from outside the building, heated and passed through the rotor. The moisture on the rotor is given up to the hot air which is then exhausted back outside the building as hot wet air. The newly-dried section of the rotor then re-emerges to the main airflow ready to adsorb more moisture. The rotor turns slowly making the operation continuous.

· The adsorption principle has important advantages. Firstly, its action is independent of temperature. An adsorption dehumidifier will operate as efficiently at -20C as +30C. Secondly the adsorption principle makes it possible to reduce the humidity levels to lower levels than condensate types. Larger adsorption dehumidifiers are permanently mounted units. However, Dry-it-Out Limited have a range of small portable completely self contained machine for domestic storage applications, such as the DD822.

· Dehumidifiers offer many advantages over alternative storage systems so it is little wonder that dehumidification is fast becoming the most popular solution to effective car storage in the UK.

· To find out more about dehumidification for your storage area contact Dry-it-Out either by telephone, fax, e-mail or by completing the enquiry form. We can provide expert advice on all aspects of car and commercial storage and supply a wide range of machines to suit all applications from small workshops to large commercial dehumidifiers. Dry-it-Out also supply dehumidification and monitoring equipment to many other commercial applications including power stations, museums, the maritime, defence and food industries and agriculture.