How to use a bivvy bag? Stupid question?

[slarge]

So, currently I live in the lap of luxury when I bivvy out, and use a laserlite tent, and want to get a bivvy bag so I can carry less gear. I only have a Rab Top bag sleeping bag (no insulation on the bottom).
Question I have is how to layer it - should it be (from the ground up): foam mat, bivvy bag, top bag; or should it be: bivvy bag, foam mat, top bag; or should it be: groundsheet, bivvy bag, foam mat, top bag?

I think the correct answer is to put the foam mat inside the top bag, and the top bag inside the bivvy bag, but then I am relying on the bivvy bag being 100% waterproof.

Thanks for your help!

[Bearbonesnorm]

Both are right (and some would argue wrong) ... much will depend on what bivvy bag you have. Some bivvy bags like std Hunka's, TN Moonlite, RAB Survival zone aren't really big enough to put a mat inside. They also don't have a heavier duty (and usually more waterproof base), so you'd really have to put your mat under the bivvy bag ... not an ideal situation when using a top bag or quilt. With one of the above bags it might also be prudent to use some sort of grounsheet to protect the base.

If you choose a different type of bivvy bag such as - RAB Storm or TN Discovery then putting your mat inside should work much better. They're bigger and usually have a heavy duty base (which might not actually be breathable) so as long as you exercise a bit of care you can often get by without an extra groundsheet ... most have the added bonus that you can fully enclose yourself if conditions get really bad. The downside is they're often heavier, bulkier and more expensive.

HTH ... although I may have just made the whole thing more complicated

[Nick]

I've not had a problem with a Hunka XL directly on the ground, loads of space inside for a mat, and my entire family probably.

[Bearbonesnorm]

I've not had a problem with a Hunka XL directly on the ground

Do most pubs not have carpet these days

[Nick]

Touche :)