Many people in your zone have great luck with a subterranean open trench dug into the ground, snow is allowed to cover and accumulate over the trees. a mesh top is fitted to deter vermin. The depth of several feet really helps keep temps regulated---however, if you have even moderately tight soil this can become a nightmare pond/ice-rink and depending on topography, often hard to load and access. I suspect your best bet is to capitalize on the waste heat from your home and heal your trees in with mulch against your foundation, preferably on the north side. You may need to make a lean-to snow deflector if snow dumping is a concern. Possibly removable. covering your trees with snow is imperative and a key to winter health, even if you must shovel your yard to do it. One thing though, while not all trees are relished by vermin, fruiting trees are. My experience is, eventually, insidious chewing vermin will descend on your trees, they always wait until they are at their very most refined state then they go crazy and chew everything to smithereens. The only known way to avoid this, if they are out of doors, is to encage them in 1/4 inch hardware cloth somehow--mothballs, peppers sprays etc, are ignored the year they decide to visit. This is why I house mine in a special wintering quarters building.