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Snow-holing in Scotland Best Practice

Snow-holing in Scotland has a long established history in both our own winter mountains and further afield. Over the last 10 years, snow-holing has grabbed the attention of the media and the viewing public. This exposure has introduced and encouraged people happy enough to pay for the experience. Andy Bateman* of Scot Mountain Holidays asks, should we assume what works in other mountains will work well in our own?

 Likely Ambient Temperature

With the seasonal minimum in some recent Scottish winters approaching -20oC and an official record of –27.3oC, you would be forgiven for assuming you’d might be sleeping in temperatures approaching those of Arctic Norway.

Yet Cairngorm (1245m) has only ever recorded around half of this at –16.5oC (12th Jan 1987). Supporting this, Coire Cais Ski Base Station (630m) has a low of -9.2oC.  The residents of nearby Nethybridge (210m) though, claimed the mercury dropped to -31.3oC on 10th January 1982. Satellite evidence suggests they were right!

The vital bit of information on these -30-ish lows are that they were all recorded during temperature inversions. The cold air flowed off the mountains and pooled in the valley bottoms where it cooled further whilst the mountain summits remained appreciably warmer. These record minima are in no way a reflection of the likely temperature you would find on our mountains. It’s not surprising when we’re never that far from a relatively warm sea in the UK!

So what temperature is likely when snow-holing in Scotland, let’s say, in the Cairngorms at around 1100m? The seasonal minimum for 900 m is usually around -8oC. At 1100 m this could translate to -10oC. Far more frequently winter temperatures at this height are around -5 and above. Our mountains simply don’t experience anything like the temperatures you might get in e.g. Arctic Norway.

 

Avoiding roof collapse or sagging

Considering the warmer temperatures when snow-holing in Scotland, do we really need snow-hole features designed to capture warm air? Are sleeping platforms and cold air drains really necessary or should our aim be to lose the warm air?

Snow is a great insulator. A meter thickness in your roof and front wall is of vital importance in this regard. That is 20 cm of insulating snow both on the exterior and interior surfaces with 60 cm of well insulated structurally sound snow. Light penetrates to a depth of around 75 cm so if you see daylight, they’re getting too thin. It should also be borne in mind that a 1 m thick roof represents a considerable weight. It’s vital the front wall is adequately thick and strong enough to support the roof.

Snow-holing in Scotland

How high is that roof? Look at the apex centre.

Avoiding Avalanches

Snow-hole sites by virtue of their high snow accumulation and steep slopes can be prone to avalanches. To be safe, you may need to pick a slope with a more gentle gradient and spend more time digging out the entrance. The majority of avalanches occur on slopes at or above 30 degrees. To maintain a 1 m thick roof, on a slope less than this, you’ll have to dig in a minimum 2+ horizontal meters from the top of the doorway before you start widening out the living area.

 

An Apex Ceiling

Avoid large areas of unsupported roof by keeping your snow-hole narrow. Aim for a depth of 2 body widths between the internal surfaces of the front and back walls.

This means you can create a relatively steep-angled apex ceiling which helps to avoid any drip points. Warm air can then be channelled towards the ventilation holes at the apex high points. In addition with it running the length of the snow-hole it increases the height with minimal snow removal giving everyone the opportunity to straighten their weary backs!

Importantly it also removes the unsupported dead weight from the ceiling. This is one of the most important aspects of snow-holing in Scotland. Although not mutually exclusive, removing the ceiling dead weight is of more importance to ceiling stability than temperature! Very few, experienced and inexperience alike, pay attention to removing the dead weight. I’ve managed to snow-hole once at +5 Deg C without any roof deformation! The roof of a snow-hole I constructed for the BBC Travel Show lasted through until around the 25th June!! The ceiling at that point was only a foot off the floor, but it hadn’t collapsed!! Every other snow-hole at that point was merely a hollow in the snow. As you create the apex be careful not to make the roof too thin. The strength of the roof is in it’s thickness.

Snow-holing in Scotland

Here you can see quite clearly the shape of the apex centre for our snowhole.

 

The all Important Ventilation

Make sure there is good ventilation. My test is to regularly watch my breath. If it drifts off to one side it’s a good indication that ventilation is adequate. Cooking with pressure stoves in a poorly ventilated snow-hole is extremely dangerous due to the formation of toxic Carbon Monoxide. All pressure stoves work by first oxidising the fuel to Carbon Monoxide (CO) and then to Carbon Dioxide (CO2). The different colours in the flame indicate this. Irrespective of good ventilation a pan of icy water can have a severe quenching effect on the flame preventing combustion of the CO. Research for the British Antarctic Survey (BAS)** showed in heating a pan of icy water CO production could be significantly reduced by raising the pan supports higher above the flame. Snow-holers should acquaint themselves with the symptoms of CO poisoning.

To put this into perspective, I’m unaware of anyone in the last 25 years dying from CO poisoning whilst snow-holing in Scotland. I do know though, instructors who’ve attributed head aches to possible CO poisoning. It’s worth considering taking a small portable CO detector with you. In a snow-hole with a single entrance and no through air movement, ventilation may well be inadequate. Extinguish candles before you go to sleep as they also produce small amounts of CO.

Although the temperature may remain around 0oC you may well still be “injecting” appreciable heat energy into the snow pack. It takes considerable heat energy to turn snow at 0oC into water at 0oC so it will not be reflected in a temperature rise. It’s far more desirable that this heat energy drifts out of the doorways than being absorbed by the snow pack.

Further ways to improve ventilation

Make it large enough to stand up in. Large communal snow-holes are less prone to an abrupt temperature rise as they have better ventilation characteristics by virtue of having several entrances, etc. An entrance walled up with blocks in combination with an open doorway will often still allow plenty of ventilation.

Putting aside the dangerous scenario of cooking in a poorly ventilated snow-hole, I’ve never got up in the middle of the night to purely unblock a doorway for ventilation reasons. All the medical research I have seen (references below) doesn’t suggest there is any potential of becoming severely hypoxic in your sleep. Studies suggest sleep will become agitated, you will awake and in doing so get up and ventilate a stuffy snow-hole.

 

Make them big

One potential hazard of digging a small snow-hole is you don’t have enough space to put the snow as you attempt to extricate yourself after a night of severe drifting. On one occasion I did have to tunnel out 1 ½ m before I hit the surface!

 

Snow-holing in Scotland: tools of the trade

When it comes Scottish snow conditions, don’t underestimate how hard the snow can get. You will need a snow shovel with a metal scoop and a good snow saw. The sintering effects of strong sunlight and hard frosts of high pressure can make wind-slab snow astonishingly hard to dig. A good snow saw is often the only effective way to deal with this type of snow.

Snow-holing in Scotland

Check out the size of the saw. It’s old fashioned but really does the job.

 

“Pack it in & pack it out”

Many of the snow-hole sites are immediately adjacent to water courses. In addition, the snow pack often lasts well into the summer meaning there’s little opportunity for biological breakdown of human waste. If you do have to go you should do your business well away from the snow-hole site and far more preferably have some system to carry it out. Cairngorm Mountain’s Snow White Project has greatly improved the situation at the Cairngorm sites. All snow-holers coming to the Cairngorms are encouraged to use it.

 

Conclusion

The safety of a snow-holing in Scotland is often a reflected by the time it has taken to dig. I’m cautious about suggesting how long digging should take as it depends on a number of factors, not least the condition of the snow. From a “duty of care” perspective I feel a large communal snow-hole is much better than several separate small ones. I normally anticipate spending 4 to 5 hrs digging a 4 plus person snow-hole. I accept in soft snow conditions that this can possibly be shorter for a fit party of 2 each digging their own entrance.

With the vagaries of the winter weather, if done correctly Snow-holing is often the far safer option compared to a tented high camp in Scotland’s Winter Mountains.

 

* Andy holds the WML and IML awards and has over 20 years Mountain Leading experience. He has guided well over 30 commercial snow-holing trips in this time and although none of the mountaineering qualifications have a remit that covers snow-holing, he is one of the few guides deemed competent by HSE criteria of “relevant experience” to run snow-holing trips.

** British Antartic Survey helped in a BSc thesis. Available on request from andrew@scotmountainholidays.com

  

Medical references:

www.ncbi.nim.ni.gov/pubmed/18665947

www.ncbi.nim.ni.gov/pubmed/9340627

www.ncbi.nim.ni.gov/pubmed/8355417

www.ncbi.nim.ni.gov/pubmed/15265339

 

Most popular self-guided hike

Lairig Ghru Logistics: a self guided hiking weekend in the Cairngorms National Park

The Lairig Ghru is the most prominent pass through the centre of the Cairngorms National Park. A road has never been built through the middle of it. It used to be a drovers’ pass for taking the cattle to market, but is now a route for walkers and cyclists to pass through the centre of the Cairngorms National Park. It runs roughly north-south from Aviemore to Braemar and is a prominent feature on the mountain skyline from Aviemore.

Lairig Ghru

Hiking into the heart of the Cairngorms

 

Photo credit: David Mansell

The main roads all circumnavigate the Cairngorms National Park which means that to drive from one side near Braemar, to the other, near Aviemore, will take close to 2 hours. To access either end of the route you’ll need to make a massive diversion on public transport via either Perth or Aberdeen, as there is no longer a bus service from Grantown on Spey to Braemar. (The Council sponsored a bus route from Grantown to Braemar – the Heather Hopper, but when funding ran out no one took the route on.)

The walking route

The route for hikers through the pass is 19 miles from Linn of Dee to Whitewell. However, if you plan to organise your own walk you’ll need to arrange for someone else to make the 2 hour diversion to the other end to meet you and take you back to your start point, or allow for the extra walk from Linn of Dee to Braemar, an additional 18 miles and perhaps the additional mile to Coylumbridge (and possibly from there to Aviemore if you miss the bus.

Lairig Ghru Scotland

Traversing the Cairngorms on the classic Lairig Ghru route, which used to be a drovers road

 

Photo Credit: Scot Mountain Holidays

The hike is 19 miles (minimum) and passes through the main Cairngorm massif under Ben Macdui, Braeriach and Carn Toul. The high point is at approximately 2000ft, so not a mean feat. The high point is within sight of Aviemore and towards the end of the south – north route we advise. You’ll finish the hike within sight of the Lairig Ghru itself.

Walk the Lairig Ghru

Self-guided Lairig Ghru logistics

Inclusive package:

Scot Mountain Holidays have put together a package for hikers to make the Lairig Ghru accessible to small groups. We can accommodate up to 8 people in our own transport, but have also arranged the trip for larger groups with additional transport. Max: 14

We offer:

The trip is very popular with couples, but priced on our website for 4 or more people. Please enquire directly with us if your group is smaller than 4 people. We’ll quote you directly.

Cairngorms - LGL options

 

Photo credit: Scot Mountain Holidays

 

Mountain Challenge:

Hiking the Lairig Ghru is a challenge in itself which anyone can complete as a charity challenge. It is a well-known and clearly defined goal familiar to most Scottish hikers, though has less of a reputation south of the border. Some mountain rescue teams already offer the route as an organised challenge event. Please contact us if you are proposing to hike the Lairig Ghru to raise funds for a charity.

Guided hike option:

We can also offer the Lairig Ghru as a guided option which might be a good option if you are on your own as we are not able to combine self-guided groups for insurance reasons. Please phone: 01479 831 331 for full details or visit our contact us page.

 

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