The solution adopted by wealthy Irish estates from the eighteenth century onward was the icehouse, a purpose-built structure designed to store blocks of ice cut from frozen ponds or rivers during winter, insulated well enough to keep them from melting through the warmer months. At Tristernagh Demesne in County Westmeath, the arrangement is unusually elaborate: not one icehouse but two, both still standing on the estate grounds roughly 150 metres north-northwest of the now-ruinous Tristernagh House.

Built around 1790, the pair are laid out on polygonal plans and differ from one another in construction details in ways that suggest they may have served slightly different purposes, or simply reflect the preferences of whoever designed them. The southern structure has a brick barrel-vaulted interior, a vaulted ceiling formed in a continuous arch along its length, with the remains of a rubble stone porch at the front, though this has largely collapsed and the entrance itself is now blocked. The northern icehouse is the better-preserved of the two: it retains a domed brick interior and a rubble stone porch with a segmental-headed doorcase, meaning a doorway topped with a shallow arched curve, positioned on the northwest side. Notably, the opening sits within the top half of the chamber rather than at ground level, an arrangement that helped trap cold air inside, since cold air sinks and a raised threshold reduced the amount that escaped each time the door was opened.

Both structures are disused, and Tristernagh House itself is a ruin, lending the whole demesne a quietly melancholy atmosphere. The icehouses survive as a reminder that refrigeration was once a luxury reserved for those with the land, labour, and capital to build and maintain it.