Underhouse insulation options

I have exposed plumbing underneath my raised house which ends up freezing in Winter time.
I would like to insulate under the house, even if it is just the plumbing itself using recycled and/or sustainable materials.
Any suggestions on how this may be done would be appreciated, particularly if you have done it already and can add some experiences.

There are a lot of possibilities. You can recycle manmade materials (Styrofoam from packaging, shredded plastics, corragulated board, old clothes) or use natural materials (natural cloth, wool, hay, straw, burlap)...
You can shield the whole underside of the house against the cooling effects of aircurrents, pack it with materials, or just insulate the plumbing.

It depends on what's available, the reason why your house is raised (groundwaterlevels, floods, pests), budget etc...

You should take care not to build a nice insulated rat or mouse (snake, raccoon etcetc) condo because then you could be trading one problem for another.

I've got a few parts of exposed plumbing. One is the greywaterflow from the upstairsbathroom. As the outside is a vertical drop I rarely get problems with it. Running the the warm tap in the morning (showering) is enough to get rid of any buildup ice over night in the winter. The other is a bit of the waterline between my house and office. It's passing trough an open attic. I insulated it with old styrofoam film that I had laying around anyway. Just to be safe I added a pipeheatingcable underneat. But that's rarely on, even in the depts of winter, so the insulation does the trick. A third is a part of the heatinglines: that's insulated with wrapped cardboard that has been painted with white chalk paint by a previous owner.

Hi Kat,
Thanks for your feedback and it sounds like there are many options I can choose from for insulation here.
I was considering polystyrene as I have some blocks of that, but I wanted to see what other people were using as well.
I understand about the risk of rats nests and that is why I have been cautious to rush into the idea straight up.

Could you add some kind of wire mesh over the insulation so that the rats don't make a nest in it ?

Hard to say without knowing your situation but I think polystyrene is a great choice for insulation situations near or touching the ground. Dont isolate the plumbing, try to connect it to the conditioned space as wrapping it may not protect it adequately. If possible, build walls or exterior insulation in a way that takes you more in the direction of a sealed crawlspace.

Thanks all for the comments!
Brian, is the use of polystyrene only for plumbing close to ground, or are you applying that principle to any insulating material?
I prefer not to isolate the whole underside of the house with walls just yet as it is also a cooling mechanism in summer time.

Not sure I know what youre asking or youre particular situation. Polystyrene in building apps is usually in the form of insulated sheathing (4x8 foot sheets of various thickness). Its not really associated with insulating plumbing. Since you enjoy some benefits of the thermal mass of the ground, my suggestion was/is to close off the space beneath your house which would make it semi-conditioned. That way, the plumbing is protected by both the ground temp and whatever energy waste is coming through your subfloor. Air sealing is critical with this strategy and if the ground beneath the home is damp, covering it with Polyethelene is advised. Also be aware that your yearly net energy bills could be worse off by having the un-insulated ground thermal mass effect.

Not knowing your situation, this could be bad advice. It might be more cost effective to use heat tape under the pipes and wrap them up with pipe insulation. The sealed, insulated crawlspace strategy would have a more holistic benefit to your home's energy costs and possibly indoor air quality.