**The attic is often a practical DIY project; insulating those exterior walls is usually a substantial renovation.** The key question is whether the plaster is directly against the block or whether there is a usable cavity behind it.

Have the inspector confirm the actual wall construction. A neighbor’s experience is a useful clue, but it doesn’t establish what this particular house contains.

For the walls, there are three possible approaches:

- **Insulate from inside.** Add a properly designed insulation and air-sealing layer, then framing or furring and drywall. This reduces room dimensions and involves adjusting window trim, baseboards, outlets, and possibly radiators or cabinets. A skilled DIYer could handle much of the carpentry and finishing, but it is a room-by-room remodeling job.
- **Insulate from outside.** Add continuous insulation and new exterior cladding. This preserves indoor space but covers the brick and requires careful detailing around windows, doors, and roof edges. It is generally a contractor-scale project.
- **Fill an existing cavity, if suitable.** This requires confirming that the cavity can safely be insulated. Don’t assume the gap behind brick is available—it may serve drainage—or that filling hollow block cores provides the same benefit as continuous insulation.

The first two approaches are described in [DOE’s masonry retrofit guidance](https://basc.pnnl.gov/resource-guides/seismic-and-insulation-retrofits-solid-masonry-walls). **Moisture design matters:** interior insulation makes the masonry colder and reduces its ability to dry inward. Depending on climate and rain exposure, a poorly designed installation can cause condensation or freeze–thaw damage. Get the wall assembly specified by someone experienced with masonry retrofits before choosing insulation or a vapor barrier. [DOE masonry insulation guide](https://www1.eere.energy.gov/buildings/publications/pdfs/building_america/enclosure-retrofit-masonry-walls.pdf)

The attic is where I would start, assuming it is an accessible, unfinished attic. The usual sequence is to seal leaks through the ceiling, maintain ventilation paths and required clearances around heat sources, then add blown cellulose/fiberglass or unfaced batts. ENERGY STAR estimates **1–3 days for a DIY attic project**, although access and preparation can make it harder. [DIY effort guide](https://www.energystar.gov/saveathome/seal_insulate/determine-effort-required), [installation guidance](https://www.energystar.gov/products/energy_star_home_upgrade/attic_insulation)

Assuming **U.S. dollars**, rough attic budgets are:

| Work | Approximate cost for 1,000 sq. ft. of attic |
|---|---:|
| DIY blown insulation, materials and equipment | $700–$1,200 |
| Professionally installed blown insulation | $1,500–$4,500 |

These are broad budgeting ranges; insulation depth, air sealing, access, removal, and repairs affect the price. [DIY cost estimate](https://costofowning.com/guides/attic-insulation-cost/), [installed cost estimate](https://www.remodelingexpense.com/costs/cost-of-attic-blown-in-insulation/)

For the walls, I would carry a **provisional five-figure renovation allowance** for a whole-house project until you obtain quotes. Insulation itself is only part of the expense; finishing, trim, electrical changes, and moisture repairs can dominate. Wall costs should be calculated using exterior **wall area**, rather than the home’s floor area.

Before purchasing, ask for measured attic insulation levels, evidence of wall dampness, and an energy assessment to prioritize improvements. If the attic contains vermiculite, leave it undisturbed pending professional assessment because it may contain asbestos. [EPA guidance](https://www.epa.gov/asbestos/my-attic-has-vermiculite-insulation-it-am-i-risk-should-i-take-it-out)

Your location, house size, and whether you intend to remodel the rooms would help narrow the wall options and budget considerably.